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Perivascular epithelioid cell tumor (PEComa) expresses melanocytic and smooth muscle markers. A man with a primary malignant cutaneous (distal left forearm) PEComa is reported. Immunohistochemistry demonstrated MiTF, HMB-45, caldesmon, desmin, and smooth muscle actin, as well as BCL1, CD10, and CD68. Next generation sequencing showed four pathogenic genomic aberrations involving BIRC3, FANCC, TP53, and TSC1 genes. His work-up was negative for metastatic disease; a wide local excision was performed. Including the reported patient, cutaneous PEComa has been described in 65 individuals: primary benign (N=58), primary malignant (N=5), and metastatic malignant (N=2). Cutaneous PEComa typically presented as a painless, slowly growing nodule oflt;2 centimeters on the lower extremity of a woman in her fifth decade. The neoplasms consisted of epithelioid cells, spindle cells, or both. The most reliable markers were MiTF (100%), HMB45 (94%), and NKIC3 (94%) for melanocytes and smooth muscle actin (43%) and desmin (40%) for smooth muscle. There has been no reported recurrence of a primary cutaneous benign or malignant PEComa after complete excision. Genomic alterations in malignant PEComas frequently involve TSC1 and TSC2 genes (mTOR activators), as well as TFE3 fusions. In November 2021, the FDA approved nab-sirolimus (mTOR inhibitor) for PEComas.

Tattoos may be associated with medical complications including, albeit rarely, skin cancer. The features of a 46-year-old man who developed a basal cell carcinoma within a tattoo on his left scapula are described and the characteristics of the other 13 patients (7 men and 6 women) with tattoo-associated basal cell carcinoma are reviewed. The tumor usually occurs on the sun-exposed skin of individuals aged 60 years and older whose tattoo has often been present for 20 years or more. The pathogenesis of a basal cell carcinoma developing within a tattoo may merely be a coincidence. However, there is supporting evidence that the tattoo and the subsequent basal cell carcinoma may be coincident events whereby either tattoo injection-associated trauma or the tattoo pigments and dyes (in their native state or after ultraviolet radiation alteration) or both have a carcinogenic impact on the development of the basal cell carcinoma at that location.

Acquired digital fibrokeratoma is a benign fibrous tumor usually located on the toes and fingers. A 63-year-old man with an acquired giant plantar fibrokeratoma is described. He presented with an asymptomatic exophytic nodule of ten years duration; there is no history of trauma to the site. It measured 15x10x5mm and was located on the plantar foot proximal to the third toe. Excisional biopsy established the diagnosis of fibrokeratoma. Giant acquired fibrokeratoma,has been described in 16 patients including ours: three women and 13 men. They are located on either the upper extremity (one man) or the lower extremity (15 individuals). Acquired plantar fibrokeratoma is rare. Including our patient, it has been reported in 11 patients: one woman and ten men. The woman was 13 years of age and the men ranged from 15 to 77-years-old. Plantar acquired fibrokeratomas are located on either the plantar aspect of the toes, the sole of the foot, or the heel. An excisional biopsy provided adequate treatment without subsequent recurrence of both giant and plantar fibrokeratomas.

A cutaneous horn, sometimes referred to as cornu cutaneum, is a projection arising on the skin due to an overgrowth of the epidermal stratum corneum. This lesion is a clinical presentation of an underlying skin tumor. A woman with a verruca vulgaris-associated cutaneous horn is described. Cutaneous horns are often solitary and appear most commonly on the face, ears, and the dorsum of the hands of older patients. The most frequent tumors associated with cutaneous horns include actinic keratoses and seborrheic keratoses; however, cutaneous horns have also been observed overlying other benign and malignant tumors. In conclusion, a cutaneous horn is a common clinical feature; however, the diagnosis of the underlying skin lesion requires a biopsy that permits adequate microscopic evaluation of the associated tumor.

Seborrheic keratosis is an epithelial-derived benign neoplasm, which presents as a solitary tumor or multiple lesions. It is an acquired skin tumor that is frequently observed in older individuals. Benign neoplasms, as well as premalignant or malignant tumors, can mimic the clinical appearance of a seborrheic keratosis. A man presented with a chronic lesion on his abdomen that had changed in the color and size. The suspected diagnosis was a seborrheic keratosis. However, the microscopic evaluation of a biopsy tissue specimen established a diagnosis of a pigmented squamous cell carcinoma in situ. In addition to squamous cell carcinoma in situ and squamous cell carcinoma, other malignant tumors, premalignant lesions, and benign lesions can mimic a seborrheic keratosis. If a patient presents with a presumptive seborrheic keratosis that has changed in appearance and for which malignancy is also suspected, a biopsy may be helpful for diagnostic clarification to either confirm that the lesion is indeed a seborrheic keratosis or to establish the diagnosis of the lesion that mimics a seborrheic keratosis.

Solitary cutaneous focal mucinosis is a unique condition defined by the presence of mucin, a hyaluronic acid complex, in the dermis. The lesion typically presents as an isolated, asymptomatic papule or nodule on the extremities or back and is not associated with any systemic condition. Conversely, multiple cutaneous focal mucinosis present with numerous skin lesions has been found to be associated with systemic diseases such as scleromyxedema, systemic lupus erythematous, and thyroid disease. Therefore, additional laboratory investigation should be considered when multiple cutaneous focal mucinosis is discovered. The case of a 37-year-old man with solitary cutaneous focal mucinosis is discussed. The skin lesion presented as an asymptomatic nodule on his right upper shoulder; microscopic evaluation established the diagnosis, and laboratory investigation was negative for any associated conditions. Similar to previous reports of solitary cutaneous focal mucinosis, our patient provides additional supporting evidence that laboratory studies for mucin-associated systemic disease are not required for individuals who present with cutaneous focal mucinosis consisting of only a solitary skin lesion.

A dystrophic nail is an alteration of the physical appearance and structural properties of the nail from its shape, color, and texture, which can result from multiple etiologies. Calcinosis cutis is a condition that refers to the calcium deposition in the skin and underlying tissue. A 55-year-old man who presented with a split right thumbnail associated with subungual calcinosis cutis affecting the same digit for a duration of nine years is described. He did not recall trauma to the affected area. Microscopic evaluation of the tissue specimen obtained following a biopsy of the affected digit's nail matrix showed foci of calcium in the dermis. The correlation of his clinical presentation and biopsy findings established a diagnosis of subungual calcinosis cutis. Subungual calcification has been observed in several clinical settings. In addition to subungual calcinosis cutis, it has been noted as a normal finding in elderly individuals. In addition, it has been observed in patients with scleroderma or following trauma to the site. Less commonly, subungual calcification can be associated with idiopathic conditions: calcifying aponeurotic fibroma, digital calcinosis circumscripta, subepidermal calcified nodule, and calcified subungual epidermoid inclusion.

Background Appropriate use criteria (AUC) provide patient-centered physician guidance in test selection. An initial set of AUC was reported by the American Society of Dermatopathology (ASDP) in 2018. AUC reflect evidence collected at single timepoints and may be affected by evolving evidence and experience. The objective of this study was to update and expand AUC for selected tests. Methods RAND/UCLA (RAND Corporation [Santa Monica, CA]/University of California Los Angeles) methodology used includes the following: (a) literature review; (b) review of previously rated tests and previously employed clinical scenarios; (c) selection of previously rated tests for new ratings; (d) development of new clinical scenarios; (e) selection of additional tests; (f) three rating rounds with feedback and group discussion after rounds 1 and 2. Results For 220 clinical scenarios comprising lymphoproliferative (light chain clonality), melanocytic (comparative genomic hybridization, fluorescence in situ hybridization, reverse transcription polymerase chain reaction, telomerase reverse transcriptase promoter), vascular disorders (MYC), and inflammatory dermatoses (periodic acid-Schiff, Gomori methenamine silver), consensus by panel raters was reached in 172 of 220 (78%) scenarios, with 103 of 148 (70%) rated "usually appropriate" or "rarely appropriate" and 45 of 148 (30%), "appropriateness uncertain." Limitations The study design only measures appropriateness. Cost, availability, test comparison, and additional clinical considerations are not measured. The possibility that the findings of this study may be influenced by the inherent biases of the dermatopathologists involved in the study cannot be excluded. Conclusions AUC are reported for selected diagnostic tests in clinical scenarios that occur in dermatopathology practice. Adhering to AUC may reduce inappropriate test utilization and improve healthcare delivery.

Urticaria is a common group of dermatologic disorders characterized by hives. Solar urticaria and heat urticaria are two rare types of chronic inducible urticarias. Solar urticaria is triggered by exposure to sunlight or ultraviolet radiation. Heat urticaria is triggered by exposure or contact with a heat stimulus. A 63-year-old woman is described who has both solar urticaria and heat urticaria and the features of these chronic inducible urticarias are reviewed. The woman presented with urticarial lesions that appeared both after exposure to the sun and after cooking at a stove. Additional history revealed she was previously diagnosed with diabetes, hypertension, and thyroid disease. After sun exposure, a punch biopsy of both the affected skin, as well as the normal-appearing skin, was done. Correlation of the clinical history, cutaneous examination, and biopsy examination confirmed the diagnosis of solar urticaria. Treatment of the patient’s urticarias included histamine 1 (H1) and histamine 2 (H2) antihistamines. Her symptoms resolved and did not recur provided that she took the medication as prescribed. Management of chronic urticaria includes not only treatment of the current episode but also prevention of future recurring urticarial lesions. In addition to antihistamines, treatment may include omalizumab (Xolair®) injections for persistent urticaria.

Verrucous xanthoma is a benign histiocytic lesion of macrophage derivation. We describe a woman with a non-mucosal verruciform xanthoma located on her right thumb and review the features of patients with verruciform acral-associated xanthoma. A 69-year-old woman presented with a lesion on her right thumb of eight years duration that had been previously treated with liquid nitrogen cryotherapy without resolution. An initial biopsy was consistent with the surface of a callous. A second biopsy demonstrated a verruciform xanthoma. The patient elected to apply lactic acid 12% twice daily and pare the lesion with a pumice stone once weekly; this resulted in flattening of the xanthoma-associated hyperkeratosis. Acral verruciform xanthoma has, albeit rarely, been described on the hands and feet of individuals. Including the patient in this report, six individuals have been reported with verrucous xanthoma on the hands and 12 individuals have been reported with a verrucous xanthoma on the feet. Verruciform xanthoma most commonly occurs on the oral mucosa. Genital lesions are also a frequent site. Acral-distributed verruciform xanthoma is rare; we propose that a verruciform xanthoma that occurs on acral sites be referred to as a verruciform acral-associated (Vacas) xanthoma.

Painful tumors of the skin present as dermal or subcutaneous nodules. They can originate from several sources: adipose tissue, cartilage degeneration, deposition of bone or calcium, eccrine glands, fibrous tissue, infiltration of benign (endometrium) or malignant (metastatic neoplasm) tissue, muscle, nerve, or vascular structures. Although pathologic evaluation of the lesion is necessary to determine the diagnosis, it is possible to make a reasonable differential diagnosis based on knowledge of prior tumors that have appeared as tender lesions. Two women with painful skin tumors - either osteoma cutis or an organizing thrombus - are described. Based on our clinical experience and review of the literature, 25 painful skin tumors were identified: chondrodermatitis nodularis helicis, angioendotheliomatosis, leiomyoma, metastases, hidradenoma, osteoma cutis, glomus tumor, fibromyxoma, leiomyosarcoma, eccrine angiomatous hamartoma, Dercum's disease, peizogenic pedal papule, neurilemmoma, angiolipoma, neuroma, dermatofibroma, granular cell tumor, endometriosis, thrombus, scar, blue rubber bleb nevus, angioma, calcinosis cutis, and keloid. An acronym - inspired by Charlotte's Web, a book that many children have read - that can be used as a memory aid for recalling the list of painful skin tumors is introduced: "CALM HOG FLED PEN AND GETS BACK".

Dermatofibromas are benign skin tumors with several variants, including the rare, uncommonly described atrophic dermatofibroma. To the best of our knowledge, there are currently 105 reported cases of atrophic dermatofibromas in the literature. This variant typically presents as a flat or depressed macule whose color can range from brown to white to red; in contrast to classic dermatofibromas that typically occur on the legs, atrophic dermatofibromas have a tendency to occur on the upper back and arms. An atrophic dermatofibroma can be clinically diagnosed; however, given the broad spectrum of clinical features of this lesion, a biopsy may be required. Characteristic pathologic features include epidermal acanthosis, basilar hyperpigmentation, fibroblast hyperplasia, and decreased or absent elastic fibers within the lesion. The pathogenesis of this lesion is not yet fully understood; however, it has been postulated that the loss of elastic fibers plays a key role in its development and characteristic atrophic appearance. We present the cases of two men with biopsy-confirmed atrophic dermatofibromas: a 47-year-old man with a pigmented macule on the right upper back and a 68-year-old man with an erythematous patch on the left posterolateral shoulder. The clinical and pathologic features of atrophic dermatofibromas are also summarized.

Kaposi sarcoma (KS) is not typically included in the differential diagnosis of lesions with clinical characteristics of pyogenic granuloma. However, cases of pyogenic granuloma-like Kaposi sarcoma have been reported in the literature. This variant is extremely rare and possesses clinical and histological findings consistent with both conditions. We report an elderly, immunocompetent man with pyogenic granuloma-like Kaposi sarcoma, which was clinically consistent with a pyogenic granuloma and possessed histological findings consistent with Kaposi sarcoma and pyogenic granuloma.

Basal cell carcinoma is the most common cutaneous neoplasm. Calcinosis cutis is the deposition of calcium within the dermis. An 80-year-old man presented with a pearly nodule on his left nasal ala; a shave biopsy confirmed the diagnosis of a nodular basal cell carcinoma with calcinosis cutis, which was removed with Mohs micrographic surgery. The incidence of basal cell carcinoma with calcinosis cutis as well as the classification, identification, and potential origin of calcium deposits in basal cell carcinoma are discussed. Basal cell carcinoma can be associated with calcinosis cutis; indeed, calcifying basal cell carcinoma has a calculated incidence of 14%. There are five categories of calcification in basal cell carcinoma. In addition, calcification observed in cancer-free initial sections of a suspected basal cell carcinoma may be a diagnostic clue that a neoplasm is present in deeper sections of the tissue specimen. Although nodular basal cell carcinoma has the greatest incidence (37%) of calcium deposition, infiltrative (29%) and micronodular (27%) basal cell carcinomas are also frequently associated with calcification; therefore, the presence of calcifying basal cell carcinoma may indicate a more aggressive tumor subtype. Basal cell carcinoma may also be suspected in the differential diagnosis of a superficial breast neoplasm in which calcification is observed in the dermis; in this situation, mammography has been an effective diagnostic approach for identifying the basal cell carcinoma with calcification. The pathogenesis of calcification in basal cell carcinoma remains to be definitively established; however, calcium-binding proteins found in poorly differentiated keratinocytes may contribute to the etiology of basal cell carcinoma with calcification. The treatment of basal cell carcinomas with calcinosis cutis is similar to that of non-calcifying basal cell carcinomas; it is based upon the histologic subtype, the size, and the location of the tumor.

Localized deposition of mucin in the upper dermis is referred to as cutaneous focal mucinosis. Patients with this condition either present with a single skin lesion (solitary cutaneous focal mucinosis) or numerous skin lesions (multiple cutaneous focal mucinosis). A man with solitary cutaneous focal mucinosis is described and the features of this condition are reviewed. Solitary cutaneous focal mucinosis has a slight male predominance and typically presents in adults, ranging in age from 29 years to 60 years, as a nodule or papule that is flesh-colored or white and most commonly located on an extremity or the trunk. Microscopic examination shows deposition of mucin in the upper dermis; the overlying epidermis can be normal, atrophic or hyperplastic. The skin lesion is often removed at the time of biopsy. However, recurrence has not been observed when the mucin deposition is present at the edge of the biopsy or excision specimen. Although the pathogenesis of this condition remains to be established, in contrast to individuals with multiple cutaneous focal mucinosis, solitary cutaneous focal mucinosis is a unique primary cutaneous mucinosis unrelated to mucinosis-associated systemic diseases.

Terbinafine is an antifungal agent used in the treatment of hair, nail, and skin dermatophyte infections. Skin side effects to terbinafine are not common. Lichenoid drug eruption is a medication-related adverse cutaneous event; the lesion morphology and pathology mimic lichen planus. A woman with onychomycosis developed a lichenoid drug eruption one week after starting terbinafine. The features of her dermatosis and the characteristics of two additional men who also experienced terbinafine-induced lichenoid drug eruption are discussed. They were receiving a daily terbinafine dosage of either 125mg or 250mg to treat onychomycosis or tinea cruris. The lichenoid drug eruption presented as diffuse or symmetric lesions within one to two weeks after starting terbinafine treatment. The extremities, chest, abdomen, and/or trunk were common sites. Less frequent locations were the lips, nails, palms, soles, and suprapubic region; lesions did not occur on the oral or genital mucosa. The eruption resolved after discontinuation of the medication (with or without treatment using topical corticosteroids, systemic corticosteroids, or both). In addition, more frequently occurring terbinafine-associated cutaneous adverse events (such as urticaria, erythematous eruptions, pruritus, acute generalized exanthematous pustulosis, subacute cutaneous lupus erythematosus, and papulosquamous conditions) are reviewed.

Tinea is a superficial fungal infection of the skin. Gyrate erythemas are reactive conditions that present as annular red lesions. A 61-year-old woman was diagnosed with tinea corporis whose skin lesions morphologically mimicked a gyrate erythema. She presented with diffuse annular plaques affecting the left side of her chest and abdomen that did not respond to a combination antifungal-corticosteroid cream for six-month duration. The appearance and clinical differential diagnosis included a gyrate erythema. Initial evaluation of the skin biopsy from the lesion’s edge demonstrated a spongiotic dermatitis, and staining for fungal organisms was negative. However, deeper sections and a different fungal stain revealed hyphae in the stratum corneum and established a diagnosis of tinea corporis. The PubMed database was used to review the following terms: tinea corporis, gyrate erythema, and tinea incognito. Relevant papers and references cited in those papers that were generated by the search were used. Tinea corporis, especially if previously treated with topical corticosteroids, can masquerade as other dermatoses including a gyrate erythema. Correlation of clinical presentation and pathology findings is essential, especially if the biopsy results do not confirm the suspected clinical diagnosis. Consideration to perform deeper sections or additional special stains or both should also be entertained when the initial pathology observations do not support the presumptive diagnosis based on clinical morphology and history.

Cellular digital fibroma is a benign fibrous lesion that typically occurred on either a finger or a toe. Cellular digital fibroma was introduced as a distinctive cluster of differentiation 34 (CD34)-positive lesion in July 2005. Cellular digital fibroma has been described in 20 patients: 12 men and 8 women. The patients ranged in age from 27 to 83 years old (median, 52 years old) at diagnosis. The tumor had been present from 2 months to 2 years (median, 11 months) prior to seeking medical attention. The cellular digital fibroma was usually slowly growing and asymptomatic; there has been no prior history of trauma at the tumor site. The lesion typically presented as either an erythematous or a flesh-colored, solitary papule of 5 mm or smaller. It frequently occurred on either the dorsal, lateral or ventral side of a digit. Yet, some of the lesions were located on the nail fold of the digit. Cellular digital fibroma shows a prominent cellular proliferation of spindle-shaped fibroblasts, without any atypia or mitoses, that extends from the papillary into the upper reticular dermis; diffuse and strongly positive CD34 staining is present throughout the entire tumor. There is no erosion by the tumor of the bony phalanx. Other acral tumors, such as superficial acral fibromyxoma (which also has diffuse strongly positive CD34 staining) and acquired digital fibrokeratoma (which is either CD34-negative or only focal CD34 positive), are in the clinical and pathologic differential diagnosis of cellular digital fibroma. Conservative complete excision is the treatment of cellular digital fibroma; however, even for tumors that have only been partially removed during biopsy, recurrence has not been observed. In conclusion, cellular digital fibroma is a unique CD34-positive acral lesion of the distal fingers and toes whose diagnosis requires correlation of the clinical morphology and the pathologic features of the tumor.

Erythroderma presents as generalized skin redness. The features of a 39-year-old man who presented with erythroderma are described. His skin biopsy revealed hyphae in the stratum corneum, which established the diagnosis of tinea corporis. His erythroderma resolved following treatment with an oral antifungal agent. Several conditions can be associated with erythroderma. Common etiologies for erythroderma include medications, neoplasms, and papulosquamous disorders. Superficial dermatophyte-associated erythroderma is rare. However, although erythroderma caused by generalized superficial mycosis is infrequently encountered, tinea corporis should be included in the new-onset or chronic erythroderma. The detection of fungal hyphae in the stratum corneum of a biopsy of the erythrodermic skin can not only establish dermatophyte infection as the underlying cause of the individual’s erythroderma but also an alternative cause of erythroderma.

Nevus sebaceus is a benign skin hamartoma of congenital onset that grows during puberty, and in adulthood can develop secondary benign and malignant neoplasms. The most common benign neoplasms occurring in nevus sebaceus are believed to be syringocystadenoma papilliferum, trichilemmoma, and trichoblastoma. A patient with nevus sebaceus developed not only syringocystadenoma papilliferum but also prurigo nodularis within her hamartomatous lesion; multiple biopsies were necessary to establish the diagnoses. Excision of the residual nevus sebaceus also revealed an apocrine cystadenoma, basaloid follicular proliferation, and sebaceoma. Also, it is important to select the appropriate biopsy site and size when evaluating a patient for secondary neoplasms within their nevus sebaceous. Indeed, more than one biopsy may be required if additional diagnoses are suspected.

Cutaneous tender tumors manifest as painful dermal or subcutaneous masses. Acronyms, a memory aid created from the initial letters of other words, can be used to assist in recalling a list of conditions. We report the case of a man who presented with a painful lesion on his leg; 15 years earlier, hot solder had embedded beneath his skin at that location. The subcutaneous mass was removed, and his symptoms resolved. Microscopic evaluation of the specimen showed a foreign body reaction to metal. Therefore, after correlating his medical history, clinical presentation, and pathology findings, the diagnosis of a foreign body (solder) and a foreign body reaction to solder, as a cause of the patient's painful skin lesion, was established. Including our patient's diagnosis for his painful skin lesion, the list of conditions that have been described as presenting as a cutaneous tender tumor include calcinosis cutis, angioendotheliomatosis, leiomyoma, metastases, hidradenoma, osteoma cutis, glomus tumor, scar, fibromyxoma, leiomyosarcoma, eccrine angiomatous hamartoma, Dercum's disease, piezogenic pedal papule, eccrine spiradenoma, neurilemmoma, something else (such as foreign body (solder) and a reaction to the foreign body), angiolipoma, neuroma, dermatofibroma, granular cell tumor, endometriosis, thrombus, blue rubber bleb nevus, angioma, chondrodermatitis nodularis helicis, and keloid. We introduce a novel acronym for painful lesions of the skin that was inspired by the book Charlotte's Web in which a barn spider (Charlotte), by weaving praises of a pig (Wilbur) into her web, is responsible for the pig's life being spared. Wilbur is a calm pig; however, there was an episode when he temporarily fled his pen and was subsequently induced, with a pail of slop, to get back into the pen. The new acronym for cutaneous tender tumors uses the initial letter of each of the 26 currently established painful skin lesions: CALM HOGS FLED PENS AND GET BACK.

Terbinafine is an antifungal agent used in the treatment of hair, nail, and skin dermatophyte infections. Skin side effects to terbinafine are not common. Lichenoid drug eruption is a medication-related adverse cutaneous event; the lesion morphology and pathology mimic lichen planus. A woman with onychomycosis developed a lichenoid drug eruption one week after starting terbinafine. The features of her dermatosis and the characteristics of two additional men who also experienced terbinafine-induced lichenoid drug eruption are discussed. They were receiving a daily terbinafine dosage of either 125mg or 250mg to treat onychomycosis or tinea cruris. The lichenoid drug eruption presented as diffuse or symmetric lesions within one to two weeks after starting terbinafine treatment. The extremities, chest, abdomen, and/or trunk were common sites. Less frequent locations were the lips, nails, palms, soles, and suprapubic region; lesions did not occur on the oral or genital mucosa. The eruption resolved after discontinuation of the medication (with or without treatment using topical corticosteroids, systemic corticosteroids, or both). In addition, more frequently occurring terbinafine-associated cutaneous adverse events (such as urticaria, erythematous eruptions, pruritus, acute generalized exanthematous pustulosis, subacute cutaneous lupus erythematosus, and papulosquamous conditions) are reviewed.

Localized deposition of mucin in the upper dermis is referred to as cutaneous focal mucinosis. Patients with this condition either present with a single skin lesion (solitary cutaneous focal mucinosis) or numerous skin lesions (multiple cutaneous focal mucinosis). A man with solitary cutaneous focal mucinosis is described and the features of this condition are reviewed. Solitary cutaneous focal mucinosis has a slight male predominance and typically presents in adults, ranging in age from 29 years to 60 years, as a nodule or papule that is flesh-colored or white and most commonly located on an extremity or the trunk. Microscopic examination shows deposition of mucin in the upper dermis; the overlying epidermis can be normal, atrophic or hyperplastic. The skin lesion is often removed at the time of biopsy. However, recurrence has not been observed when the mucin deposition is present at the edge of the biopsy or excision specimen. Although the pathogenesis of this condition remains to be established, in contrast to individuals with multiple cutaneous focal mucinosis, solitary cutaneous focal mucinosis is a unique primary cutaneous mucinosis unrelated to mucinosis-associated systemic diseases.

Malassezia (Pityrosporum) folliculitis usually appears as pruritic monomorphous papules and pustules on the upper back, chest, extensor arms and face. Acne vulgaris, bacterial folliculitis, eosinophilic folliculitis and systemic corticosteroid-induced acne can clinically mimic the fungal-caused acneiform condition. The designation incognito is used to describe tinea or scabies when the characteristic presentation is masqueraded by the application of topical corticosteroid treatment. Application of corticosteroid cream altered the morphology of the skin lesions in a man with Malassezia folliculitis. His cutaneous findings-localized areas of post-inflammatory hyperpigmentation with flattened or completely resolved follicular papules-raised the possibility of partially treated follicular eczema or follicular contact dermatitis. Pathognomonic findings from biopsies of the skin lesions established the diagnosis of Malassezia folliculitis; the condition completely resolved after treatment with topical antifungal shampoo and cream. Similar to tinea incognito and scabies incognito, folliculitis caused by Malassezia yeast in which the cutaneous morphology has been concealed by management with topical corticosteroids should be referred to as Malassezia (Pityrosporum) folliculitis incognito.

Nevus sebaceus is a benign skin hamartoma of congenital onset that grows during puberty, and in adulthood can develop secondary benign and malignant neoplasms. The most common benign neoplasms occurring in nevus sebaceus are believed to be syringocystadenoma papilliferum, trichilemmoma, and trichoblastoma. A patient with nevus sebaceus developed not only syringocystadenoma papilliferum but also prurigo nodularis within her hamartomatous lesion; multiple biopsies were necessary to establish the diagnoses. Excision of the residual nevus sebaceus also revealed an apocrine cystadenoma, basaloid follicular proliferation, and sebaceoma. Also, it is important to select the appropriate biopsy site and size when evaluating a patient for secondary neoplasms within their nevus sebaceous. Indeed, more than one biopsy may be required if additional diagnoses are suspected.

Background: The placement of a tattoo is a common event. Basal cell carcinoma arising from a tattoo is rare despite this neoplasm being the most common form of skin cancer. Objective: We describe a 41-year-old man who developed a basal cell carcinoma in his tattoo and review the literature of basal cell carcinomas originating in a tattoo. Methods: A literature search using PubMed was performed. The following terms were searched: “basal,” “carcinoma,” “cell,” and “tattoo.” The characteristics of individuals with a basal cell carcinoma originating in a tattoo were analyzed and summarized. Results: A total of 13 patients (6 women and 7 men) with a basal cell carcinoma arising in a tattoo have been reported. The majority of the tumors were located on the head (6 cases, 46.2%) followed by either an upper extremity (4 cases, 30.7%) or the trunk (3 cases, 23.1%). Most of the carcinomas were asymptomatic; however, 2 patients reported pruritus associated with their tumor. Nodular basal cell carcinoma was the most common subtype diagnosed (5 tumors), followed by superficial basal cell carcinoma (2 tumors). One patient had either a pagetoid or a mixed (nodular and sclerosing) histology. The pathological variant was not described for 4 patients. Conclusions: Basal cell carcinoma arising in a tattoo is a rare occurrence. Although this occurrence may be coincidental, emerging evidence of carcinogenesis associated with tattoo pigment may suggest a causal link. Elucidating this important relationship warrants further investigation.

Osteoma cutis is a benign cutaneous lesion characterized by the presence of bone within the dermis or subcutaneous fat. It most often develops in association with other skin lesions such as cutaneous tumors. Nevus sebaceus is a benign hamartoma of the skin that is composed of epidermal and dermal components. It most commonly appears on the scalp and may give rise to either benign or malignant secondary neoplasms. The clinical and pathologic features of a 36-year-old man with a nevus sebaceus and associated osteoma cutis are described. In addition, osteoma cutis-associated neoplasms are reviewed. Secondary osteoma cutis has been observed with both benign and malignant neoplasms as well as various non-neoplastic skin conditions. However, to the best of our knowledge, osteoma cutis has not previously been described in association with nevus sebaceus. Nevus sebaceus can now be added to the list of cutaneous osteoma-associated skin tumors (COASTs).

Melanoma may occur during or after natural or in vitro fertilization-associated pregnancy. A 43-year-old woman, who had received in vitro fertilization and developed a melanoma five months postpartum is described. Some studies have not shown in vitro fertilization to increase melanoma risk; however, several investigations have observed melanoma risk to be greater in women who have had this treatment. Therefore, although a potential increased risk for melanoma has been observed in infertile women who were either pregnant before or following in vitro fertilization, whether in vitro fertilization is an etiologic risk factor in the pathogenesis of melanoma for these individuals-or is merely a coincidental event-remains to be established.

Melanoacanthoma is a benign epithelial tumor composed of melanocytes and keratinocytes that can morphologically mimic malignant neoplasms. Two patients with melanoacanthoma that clinically masqueraded as melanoma are described: a 65-year-old African-American woman with a pigmented nodule on the right preauricular area and an 85-year-old Haitian-Creole man with a large exophytic nodule on his left lower abdomen. Melanoma was clinically suspected in both patients. Biopsies were performed, which established the diagnosis of melanoacanthoma. Complete removal of a melanoacanthoma should be considered since partial excision may result in recurrence.

Pigmented actinic keratosis is an uncommon variant of actinic keratosis that can mimic melanocytic lesions. A 54-year-old man who presented with a dark lesion on his nasal tip is described; biopsy of the lesion revealed a pigmented actinic keratosis that was treated with cryotherapy using liquid nitrogen. Pigmented actinic keratoses typically appear on sun-exposed areas of the skin as flat hyperpigmented lesions that grow in a centrifugal pattern. Dermoscopy reveals one or more pseudonetworks with hyperpigmented dots or globules. Histopathology shows atypical keratinocytes in the epidermal basal layer and increased melanin content in the epidermis and dermis. Treatment options include liquid nitrogen cryotherapy for solitary lesions and curettage, 5-fluorouracil, imiquimod, ingenol mebutate, photodynamic therapy, or superficial peels for extensive lesions.

Osteoma cutis can occur as a primary or secondary cutaneous lesion. Isolated lesions of perforating osteoma cutis are uncommon and can present with varying clinical features. Adverse events that can occur following placement of a tattoo include benign and malignant neoplasms, dermatoses, infections, and miscellaneous complications. We present a case of a man who developed perforating osteoma cutis within a tattoo and propose that osteoma cutis be included among the list of adverse events that can occur in individuals who obtain a tattoo.

Allergic contact dermatitis (ACD) is a type IV (delayed) hypersensitivity reaction that has a wide spectrum of presentations that often imitate or overlap with other cutaneous eruptions. Differential diagnoses to consider include infections, skin lymphoma-malignancies, inflammatory dermatoses, nutritional deficiencies, and mechanical causes of tissue damage. We discuss clues to the diagnosis of ACD, such as pruritus, localization to the area of skin contact with the allergen, recurrence with repeat exposures, and supportive skin biopsy histology. Epicutaneous patch testing remains the gold standard for diagnosing ACD. Definitive treatment is contact allergen avoidance and, when indicated, dietary restriction. With these measures, most patients will improve clinically. In cases where avoidance measures and interim topical therapies fail, ultraviolet light therapy or systemic immunosuppression may be considered. Key points 1. Allergic contact dermatitis (ACD) is a type IV (delayed) hypersensitivity reaction with a range of clinical presentations. 2. Mimickers of ACD include infections, skin lymphoma-malignancies, inflammatory dermatoses, nutritional deficiencies, and mechanical causes of tissue damage. 3. Allergen avoidance, which might include dietary restriction, is the definitive treatment for ACD.

Poly-l-lactic acid (Sculptra, Sanofi Aventis, Bridgewater, NJ) is a gel polymer made of poly-l-lactic acid microspheres and water suspended in a mannitol and carboxymethyl cellulose suspension.1 This injectable tissue filler has been used for correction of lipoatrophy in HIV patients as well as for cosmetic purposes since its US Food and Drug Administration approval in 2004. The mechanism of action involves induction of a subclinical inflammatory response that stimulates fibroblast proliferation and collagen formation, ultimately leading to a progressive increase in volume of the dermis and subcutaneous tissues.2 Late-onset immune-mediated adverse effects associated with the use of poly-l-lactic acid can appear years after the initial injection with reported range of 6 to 60 months.3 These effects include inflammatory nodules, papules, and edema. Previous reports of adverse effects associated with poly-l-lactic acid identify a maximum of 60 months before development of a subcutaneous nodule.3 These adverse effects can cause significant distress for patients, as the erythema, edema or nodules that can result may cause cosmetic disfigurement and mimic an infectious process, necessitating, at times, extensive workup including biopsy. Here, we present a case of granuloma formation that appeared more than 70 months after treatment, surpassing the previously reported maximum latency of 60 months for poly-l-lactic acid and long surpassing the 2-year duration that the product is purported to last in the tissues.1 To our knowledge, this is the longest reported latency period for development of a subcutaneous nodule with foreign body reaction observed with poly-l-lactic acid. Practitioners should be aware of the extent of adverse events associated with procedural complications to adequately inform their patients, provide the highest standard of care, and maintain awareness of this etiology in their differential diagnosis for patients presenting with facial nodules of unknown etiology, even if poly-l-lactic acid exposure was several years prior.

Introduction: An innovative skincare product line incorporating a proprietary blend of selected peptides and botanicals formulation has been developed with the aim of preparing skin surfaces for rejuvenating procedures and for their long-term maintenance. The premise is to clear the extracellular matrix (ECM) of accumulated waste products improving cellular ECM cross talk enabling efficient collagenesis and elastogenesis to follow. Methods: To validate this scientific narrative and examine efficacy without the use of rejuvenating devices, we have undertaken a series of histological examinations in 5 subjects in their 60s assessing changes following isolated topical application of product to the skin. Results: From a histological perspective, our findings showed significant changes within the ECM, with new collagen formation and increased elastin, a ‘healthier’ epidermis with healthy cuboidal basal stem cells at the dermoepidermal junction, a thickened epidermis and increased procollagen levels within the newly created ECM. This was evident in all patients in varying degrees. Conclusion: It is apparent that in periods as short as 3 weeks, histological changes can be initiated purely by topical application of this proprietary blend of peptides and botanicals. This validates the use of these products as preconditioning for procedures and in conjunction with the use of rejuvenating devices

A psoriasis-like eruption develops in a subset of patients with Kawasaki disease (KD).We sought to systematically compare KD-associated psoriasiform eruptions with classic psoriasis and the outcomes of KD in children with and without this rash.This was a retrospective study of 11 KD cases with a psoriasiform eruption matched 1:2 by age, gender, and ethnicity with psoriasis-only and KD-only controls. Genotyping was performed in 10 cases for a deletion of 2 late cornified envelope (LCE) genes, LCE3C_LCE3B-del, associated with increased risk for pediatric-onset psoriasis.Similar to classic psoriasis, KD-associated eruptions were characterized clinically by well-demarcated, scaly pink plaques and histopathologically by intraepidermal neutrophils, suprabasilar keratin 16 expression, and increased Ki-67 expression. They showed less frequent diaper area involvement, more crust and serous exudate, and an enduring remission (91% vs 23% with confirmed resolution; P .001). Frequency of LCE3C_LCE3B-del and major KD outcomes were similar between cases and controls.The study was limited by the small number of cases, treatment variation, and availability of skin biopsy specimens.Although the overall clinical and histopathologic findings were similar to conventional psoriasis, this appears to be a distinct phenotype with significantly greater propensity for remission. No adverse effect on KD outcomes was noted.

Dermal melanocytosis is a benign phenomenon most commonly noted in people with darkly pigmented skin. Multiple entities with dermal melanocytosis are described, including Mongolian spot, nevus of Ota, nevus of Ito, nevus of Hori, and acquired dermal melanocytosis. We report a case of acquired dermal melanocytosis occurring in a 42-year-old Hispanic man with psoriasis treated with infliximab for 9 months. The patient presented with an isolated pigmented patch on his left dorsal hand. Histopathologic examination of the skin revealed numerous dendritic, heavily pigmented melanocytes in the papillary and upper reticular dermis. We review the literature and discuss the pathogenesis of acquired dermal melanocytosis.

Dermal melanocytosis is a benign phenomenon most commonly noted in people with darkly pigmented skin. Multiple entities with dermal melanocytosis are described, including Mongolian spot, nevus of Ota, nevus of Ito, nevus of Hori, and acquired dermal melanocytosis. We report a case of acquired dermal melanocytosis occurring in a 42-year-old Hispanic man with psoriasis treated with infliximab for 9 months. The patient presented with an isolated pigmented patch on his left dorsal hand. Histopathologic examination of the skin revealed numerous dendritic, heavily pigmented melanocytes in the papillary and upper reticular dermis. We review the literature and discuss the pathogenesis of acquired dermal melanocytosis.