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Context.— Syringocystadenocarcinoma papilliferum (SCACP) is a rare adnexal carcinoma and the malignant counterpart of syringocystadenoma papilliferum (SCAP), which is commonly located on the head and neck and may arise in association with a nevus sebaceus. RAS mutations have been identified in both SCAP and nevus sebaceus. Objective.— To evaluate the clinicopathologic and molecular features of SCACPs, which have not been previously explored. Design.— We obtained 11 SCACPs from 6 institutions and reviewed the clinicopathologic features. We also performed molecular profiling using next-generation sequencing. Results.— The cohort comprised 6 women and 5 men with ages ranging from 29 to 96 years (mean, 73.6 years). The neoplasms occurred on the head and neck (n = 8; 73%) and extremities (n = 3; 27%). Three tumors possibly arose in a nevus sebaceus. A total of 4 cases showed at least carcinoma in situ (adenocarcinoma, n = 3; squamous cell carcinoma [SCC], n = 1), and 7 cases were invasive (SCC, n = 5; mixed adenocarcinoma + SCC, n = 2). A total of 8 of 11 cases (73%) identified hot spot mutations consisting of HRAS (n = 4), KRAS (n = 1), BRAF (n = 1), TP53 (n = 4), ATM (n = 2), FLT3 (n = 1), CDKN2A (n = 1), and PTEN (n = 1). All 4 cases with HRAS mutations occurred on the head and neck, whereas the KRAS mutation occurred on the extremity. Conclusions.— RAS-activating mutations were detected in 50% of the cases, of which most (80%) involved HRAS and occurred on the head and neck, which shows overlapping features with SCAP, supporting that a subset may arise as a result of malignant transformation and likely an early oncogenic event.

Spitzoid melanocytic neoplasms are well known to be diagnostically challenging. Immunohistochemistry (IHC) and molecular approaches have been used as ancillary diagnostic tests. Herein, we investigate the use of PRAME IHC for the assessment of spitzoid melanocytic neoplasms.Ten Spitz nevi, 14 atypical Spitz tumors, and 11 spitzoid melanomas were retrieved, and PRAME IHC was scored on a scale of 1-4 (in % quartiles). Intensity of staining was categorized as weak or strong. Cases with no staining received a score of 0. Positive lymph nodes from three spitzoid melanomas were also analyzed.Spitz nevi, atypical Spitz tumors, and spitzoid melanomas had mean PRAME IHC scores of 1.20, 0.93, and 3.36, respectively. The percentage of cases with a score 3 or higher for each category of spitzoid neoplasms are as follows: Spitz nevus (20%), atypical Spitz tumor (0%), and spitzoid melanoma (82%). Among the spitzoid melanomas, three cases had positive sentinel lymph nodes, which showed PRAME score of 2, 4, and 4 in the metastatic deposits.Previous reports revealed PRAME IHC as useful tool to distinguish benign from malignant melanocytic lesions. The results presented here are concordant with the prior studies, but expand the application of this marker to Spitz nevi/tumors and spitzoid melanomas. The present findings suggest the potential diagnostic utility of PRAME IHC in the assessment of spitzoid melanocytic lesions, particularly in distinguishing spitzoid melanomas from Spitz nevi and atypical Spitz tumors.

Mesenchymal tumors harboring GLI1 gene abnormalities are a rare but distinctive group of neoplasms whose clinicopathologic features are currently evolving. In particular, examples of this tumor with ACTB-GLI1 gene fusion, tentatively termed ACTB-GLI1 epithelioid mesenchymal neoplasm (EMN), show a distinctive monomorphic round-to-epithelioid morphology, nested to trabecular pattern of growth, and S100+/SOX10-/SMA- immunophenotype. We report the first case of this entity arising exclusively in the skin. A 69-year-old man with no prior history of neoplasia presented with a 1.5-cm raised lesion on the left buttock. Histopathologic examination revealed a diffuse dermal proliferation of small, monomorphic, round-to-ovoid cells with hyperchromatic nuclei, focally enlarged nucleoli, and minimal eosinophilic to clear-staining cytoplasm. These cells were arranged in confluent nests and trabeculae in a background of fibrocollagenous to focally myxoid stroma. Immunohistochemical analysis revealed strong positivity for S100 and CD56, and negativity for SOX-10, SMA, Melan-A, HMB-45, and a variety of other markers. Based on the morphology and immunophenotype, molecular studies were performed, which revealed the presence of an ACTB-GLI1 fusion transcript, confirming the diagnosis. Given the morphologic overlap of this tumor with other cutaneous round cell neoplasms and its potential for malignant behavior, ACTB-GLI1 EMN is an important entity for pathologists to recognize.

Immunohistochemistry is useful and often necessary for the diagnosis of many histopathological entities, including atypical fibroxanthoma (AFX), which is typically considered a diagnosis of exclusion after ruling out spindle cell melanoma, sarcomatoid carcinoma, and other spindle cell tumors. AFX is a superficial fibrohistiocytic tumor previously believed to be related to pleomorphic sarcoma (formerly known as malignant fibrous histiocytoma), but is now considered a distinct clinicopathological entity. AFXs commonly express CD68, smooth muscle actin, and lysozyme and are usually negative for melanocytic markers such as HMB45 and S100. However, immunohistochemistry can sometimes be misleading, especially when used without other relevant markers in making a histopathologic diagnosis. HMB45 is a glycoprotein marker of premelanosomes and is often helpful in identifying melanoma because it stains melanosomes in the epidermis, dermis, and nevi glycocomplexes. We report a case of AFX which was strongly positive for HMB45, but negative for all other melanocytic markers. This case emphasizes the potential pitfall of relying on a single immunohistochemical marker to make the diagnosis, especially of melanoma, and also is one of the only rare reported cases of AFXs which are HMB45+.

A 76-year-old female patient presented with a peculiar new exophytic-appearing, flesh-colored skin lesion on her left hallux. Owing to its atypical appearance, the neoplasm was biopsied. Histologic sections demonstrated numerous thickened, anastomosing cord-like structures composed of bland appearing adnexal keratinocytes attached to the epidermis and extending into the superficial dermis. Nearby areas exhibited papillomatosis, epidermal acanthosis, dense hyperparakeratosis, hypergranulosis, and superficial koilocytes, findings consistent with a verruca plantaris. A p16 stain was positive in many of the superficial epidermal keratinocytes. Human papillomavirus typing by in situ hybridization for the most common low-risk and high-risk types was also performed and was negative for these. We herein present an unusual case of a skin lesion which combines features of a poroma with a verruca plantaris. We further review what is known of the relationship between human papillomavirus and poroid neoplasms.

Cranial fasciitis is a rare cause of a painless, progressive skull mass in the pediatric population, having been described in only 80 cases in the literature to-date. While the etiology remains unknown, the pathogenesis is thought to be a reactive process causing a non-neoplastic fibroblastic proliferation arising from the deep fascia or periosteum of the cranium. Accurate diagnosis may be delayed due to the lack of physical signs and symptoms on presentation, as well as equivocal imaging for the other lesions included in the differential diagnosis. Importantly, in the case of cranial fasciitis, involved tissue is hard to decipher from normal tissue in the cranium, and margin recommendations have not yet been made clear in the current literature. Herein, we present a case of confirmed cranial fasciitis in a 2-year-old female patient in whom frameless stereotaxy was used intraoperatively to determine the extent of the lesion and ensure adequate resection and minimize recurrence risk.

Ossifying plexiform tumor is an exceedingly rare cutaneous neoplasm with distinctive histologic features. The typical microscopic appearance is that of a well-circumscribed dermal lesion composed of spindled and epithelioid cells in a myxoid appearing matrix with a plexiform architecture associated with areas of ossification. The present report details the clinicopathologic features of an ossifying plexiform tumor involving the lower extremity of a 69-year-old man. The cutaneous lesion exhibited characteristic morphologic features of this entity. By immunohistochemistry, the tumor was negative for most markers assessed, but notably exhibited diffuse positivity for SATB2. No lesional recurrence was observed. The present case serves to expand on the limited existing knowledge regarding the clinicopathologic features of this uncommon tumor. The histogenesis of ossifying plexiform tumor remains unclear; however, the demonstration of SATB2 expression in this case suggests osteoblastic differentiation.

Rosai-Dorfman disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is a rare disease typically characterized by a histiocytic proliferation within lymph nodes, which is due to an unknown etiology. Extranodal involvement can occur, and it more rarely can involve the skin. RDD generally presents with an indolent nature and follows a benign disease course, although more aggressive cases have been reported. The condition predominately affects children and young adults. It is classically characterized by massive, bilateral painless lymphadenopathy and accumulation of CD68-positive, S100-positive, CD1a-negative histiocytes, with the presence of emperipolesis as a hallmark. Herein, we present an aggressive case in a 76-year-old male with past medical history significant for prostate cancer, who presented with a 7-month history of lymphadenopathy and new onset of multiple large abdominal wall, cutaneous, lymph node, liver, and lung masses, all of which were histopathologically atypical, but showed features consistent with RDD, including emperipolesis and strong S100 positivity. Molecular studies showed a KRAS 117N mutation, which has been recently reported in RDD. While most cases present as a benign tumor, this case demonstrated aggressive features clinically, showed partial response to MEK inhibitor immunotherapy in the setting of a KRAS mutation, and demonstrated atypical cytologic features on histopathology.

The epidermal basement membrane (BM) is readily identified on skin biopsy specimens stained with periodic acid-Schiff (PAS) and PAS with diastase (PAS-D). Thickening of BM can be evidenced in several inflammatory and tumoral conditions. We noticed that most of our biopsy specimens of mycosis fungoides (MF) showed thickening of the BM. We decided to retrospectively study BM thickness in 27 biopsy specimens of MF and compare them with 27 cutaneous biopsy specimens of inflammatory diseases. We studied PAS and PAS-D stains in all cases and we measured BM thickness with an ocular micrometer. Cases were scored in a four-tiered system: 0: no detectable staining; 1+ (mild: 5 μm); 2+ (moderate: 5-9 μm); and 3+ (prominent:9 μm). The difference between both groups (MF vs controls) was highly significant for BM thickness values by both one- and two-tailed t tests (P 0.0006). While only 3 biopsy specimens from the controls (11.11%) showed areas of 3+ thickening, 12 biopsy specimens of MF (44.44%) showed areas of 3+ thickening, and most cases showed diffuse, at least 2+ thickening, while the controls showed more segmental, mostly 1 or 2+ staining. We conclude that thickening of BM can be useful in the differential diagnosis with inflammatory conditions.

Porocarcinoma is an infrequent malignant adnexal carcinoma, with some histopathological variants described, such as the clear cell, the sarcomatoid or the pigmented porocarcinoma. We report an invasive porocarcinoma showing areas of tumor cells floating in prominent dermal mucin, simulating mucinous carcinoma, that we consider a new histopathological variant of porocarcinoma. We report a 74-year-old male with previous history of multiple basal cell carcinomas that presented a nodule on his left temple. Histopathologic study showed a large ulcerated multilobular tumor composed of thickened cords of cells emanating from a hyperplastic epidermis and showing a mixed infiltrative and pushing pattern in the dermis. Poroid differentiation was observed in most of the neoplasm, both in intraepidermal and dermal invasive component. Within the neoplasm a prominent area where these small nests with clear formation of ducts were floating in mucinous pools with few septa intermingled was observed, simulating a primary cutaneous mucinous carcinoma. Cytology, immunohistochemistry and the presence of both neoplastic areas as closely related and with multiple points of connectivity favors the consideration of a composite tumor in this peculiar case. Other differentials are discussed.

Aim: Evaluate the accuracy of a 23-gene expression signature in differentiating benign nevi from melanoma by comparing test results with clinical outcomes. Materials & methods: Seven dermatopathologists blinded to gene expression test results and clinical outcomes examined 181 lesions to identify diagnostically uncertain cases. Participants independently recorded diagnoses and responses to questions quantifying diagnostic certainty. Test accuracy was determined through comparison with clinical outcomes (sensitivity and percent negative agreement). Results: Overall, 125 cases fulfilled criteria for diagnostic uncertainty (69.1%; 95% CI: 61.8–75.7%). Test sensitivity and percent negative agreement in these cases were 90.4% (95% CI: 79.0–96.8%) and 95.5% (95% CI: 87.3–99.1%), respectively. Conclusion: The 23-gene expression signature has high diagnostic accuracy in diagnostically uncertain cases when evaluated against clinical outcomes.

Syphilis is a sexually transmitted disease caused by Treponema pallidum. The primary stage of the disease (the chancre) mainly involves the genital areas. Extragenital areas are involved in 5%-14% of cases, many of which occur in the oral cavity. Among the extragenital locations, the lip is the most frequent; however, despite this, published cases of the chancre of the lip are few. We present a case of a chancre presenting on the lip of a nonimmunocompromised 55-year-old male patient with immunohistochemical confirmation.

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.

A 47-year-old white man presented with a 14-month history of an asymptomatic 2-cm, slow-growing nodular lesion on his left shin that arose in the background of a black tattoo. An excisional biopsy followed by histological examination revealed a prominent lymphohistiocytic infiltrate, with many large, foamy histiocytic cells containing intact inflammatory cells within their cytoplasm, findings consistent with emperipolesis, a feature typical of Rosai-Dorfman disease (RDD). By immunohistochemistry, S-100 (a marker that is positive in almost all cases of RDD) was negative, arguing against the diagnosis of RDD. In addition, prominent black tattoo pigment was seen in many areas, expanding the differential diagnosis to include an unusual reactive lymphohistiocytic response to the tattoo mimicking RDD. Histologically, RDD shows many plasma cells, neutrophils, lymphocytes, and histiocytes with abundant foamy cytoplasm that contains intact lymphocytes and other cells, a phenomenon described as emperipolesis. A wide variety of cutaneous reactions to tattoos have been described, including tenderness, burning pain, inflammation, and pruritus. However, histologic features suggestive of RDD as a reaction to tattoo pigment have not been previously described and should therefore also be considered as a potential rare reaction pattern to tattoos.

A neurofibroma is a benign neural tumor arising within a peripheral nerve sheath composed of Schwann cells, fibroblasts, and immune cells involved in the nerve. Microcystic elements have been rarely described in these tumors. Neurofibromas are classically described as unencapsulated tumors of interspersed spindle cells and mast cells in a hypocellular, myxoid stroma. These tumors are most commonly dermal and seen in almost all patients with neurofibromatosis type 1; however, they may also occur sporadically, as seen in our case here. We report a 23-year-old patient with no significant medical history who presented with a dome-shaped papule on her cheek. This slow-growing mass had been present for multiple years and was soft, inflamed, and painful. Shave biopsy was collected and sent for evaluation. The shave biopsy diagnosed a benign neural tumor with features of a rare microcystic neurofibroma. This unencapsulated tumor consisted of microcystic spaces lined by oval-shaped to spindle-shaped cells in a matrix of myxoid to collagenous-like areas. Scattered lymphocytes and mast cells were noted, with few true vessels enclosing red blood cells. The stromal cells and cells lining the microcystic spaces stained S100 and SOX-10 positive. These cells had limited CD34 staining; however, most microcystic spaces were negative. Only the few true vessels stained CD31 positive. It is important to distinguish the prominent microcystic features in neurofibromas versus schwannomas by the lack of encapsulation or Antoni A features with Verocay bodies, which are typical of the latter. Further differentiating neurofibromas versus malignant peripheral nerve sheath tumors is required, where the latter should exhibit much greater nuclear atypic, higher cellularity, necrosis, hemorrhage, and increased mitotic activity. Excision of this benign microcystic neurofibroma was not deemed necessary because of lack of clinical concern and recurrent lesions.

Cutaneous intestinal either metaplasia or ectopia has mostly been described around intestinal stomas or in patients with Crohn disease. In this study, we described a unique case of cutaneous metaplasia on the elbow of a 25-year-old man who had a clinical history of epidermolysis bullosa simplex, but had no history of any gastrointestinal disease. The lesion had been clinically stable for 5 years. Histopathologically, the epithelium showed many columnar cells with mucinous cytoplasm, with no atypia or mitoses. The proliferation rate was low (7% by Ki67). The metaplastic areas expressed epithelial membrane antigen, carcinoembryonic antigen, cytokeratin 7, MUC5AC, MUC2, and Cyclin-D1.

Immunohistochemistry (IHC) for p16 has been evaluated in melanocytic lesions,with most nevi exhibiting positivity for p16 while melanomas are more likely to show loss of p16 expression.1 This difference in expression has led to the use of p16 immunohistochemistry as a diagnostic marker for the distinction of nevi from melanoma.2 In a prior study, we analysed p16 expression in nevi of pregnancy, with particular emphasis on evaluating the potential utility of p16 as marker to distinguish these lesions from nevoid melanomas. The majority of nevi from pregnant patients demonstrated significant p16 positive immunohistochemical staining, while most nevoid melanomas showed significant loss of p16 expression.3 Since nevi from pregnant patients may display unusual morphological features4 that could potentially lead to a misdiagnosis, in particular nevoid melanoma, the results of our investigation supported use of p16 as an adjunctive diagnostic tool to distinguish between these lesions. One limitation of the prior study was lack of long-term clinical outcome data. Herein, we present clinical follow-up analysis exploring the relationship between p16 expression and clinical outcome in patients with nevi of pregnancy and nevoid melanoma. Cases, as previously reported, consisted of 14 nevi and 20 patients with melanoma. Clinical follow-up data of the patients were obtained through our electronic medical record system. Recurrence or metastasis, number of months of follow-up, living or deceased status, chemotherapy treatment, and other pertinent information were gathered. …

Distinction of superficial spreading melanoma (SSM) from compound nevi (CN) sometimes poses difficult diagnostic challenges. Herein, we studied cyclin D1 protein expression by immunohistochemistry in SSM and CN and evaluated the results by digital image analysis.A total of 13 CN and 12 SSM cases were retrospectively reviewed and cyclin D1 immunohistochemistry was performed. Immunohistochemical stained slides were evaluated by digital imaging analysis that included quantification and staining intensity of the cyclin D1 expressing dermal cells.Cyclin D1 expression was observed in all CN and SSM. CN-positive staining was present in 30% to 93% of the dermal nevocytes, more positive in the upper (mean 85%), than lower half (mean 57%). SSM-positive staining was present in 44% to 96% of the dermal lesion, more positive in the upper (mean 88%) than lower half (mean 49%). When analyzed based on 3+ strong staining intensity, similar regional differences in cyclin D1 expression were observed.Digital image analysis of Cyclin D1 expression showed no differences between CN and SSM. Quantity and regional distribution of cyclin D1 positivity were found to be similar in both lesions. Our findings argue against the routine use of cyclin D1 immunohistochemistry as a diagnostic tool for differentiating CN from SSM.

Tattoos are a common practice in the 21st century. Although most modern pigments are organic and made of vegetable or plastic compounds, they still sometimes elicit an adverse reaction in the skin. Identifying the tattoo pigment in such biopsies is not always an easy task. To study how tattoo inks appear in the skin, we injected 14 different colors of commercial tattoo ink into normal skin obtained from a mastectomy specimen. One unstained section was obtained from each case, as well as one section stained with hematoxylin-eosin from each case. All sections were observed under the microscope. Stained and unstained sections were also examined under polarized light. We did not observe any modification of the ink color with the staining process with hematoxylin-eosin. However, some pigments appeared differently in stained and unstained sections than in the vial. Pink was the most difficult color to identify from the eosinophilic tissue. None of the colors showed any birefringent particles. However, in some unstained slides under polarized light, the color of the pigment appeared more similar to the one in the vial than in the stained slide.

The American Society of Dermatopathology has established an Appropriate Use Criteria (AUC) Committee with the intention of establishing evidence-based recommendations regarding the appropriateness of various ancillary tests commonly utilized by dermatopathologists. Periodic acid Schiff (PAS) and Grocott (or Gomori) methenamine silver (GMS) stains represent some of the most commonly employed ancillary tests in dermatopathology. The utility of these tests was targeted for evaluation by the AUC. This literature review represents a comprehensive evaluation of available evidence for the utility of PAS and/or GMS staining of skin and nail biopsies. In concert with expert opinion, these data will be incorporated into future recommendations by the AUC for PAS and GMS staining in routine dermatopathology practice.

Introduction Mature sebaceous glands do not contain Merkel cells. Neither do sebaceous tumors in the vast majority of cases. Recently, however, it was showed that rare sebaceous adenomas with a carcinoid-like or labyrinthine pattern can contain intratumoral Merkel cells. Our purpose in this study is to examine for the presence of Merkel cells in extraocular sebaceous carcinomas. Methods Nineteen cases of extraocular sebaceous carcinoma were retrospectively studied with cytokeratin 20. Results One out of 19 cases (5.3%) contained Merkel cells in the basal layers of the tumoral nests of a sebaceous carcinoma from the cheek of a 76-year-old woman. Conclusions Merkel cells are rarely evident in extraocular sebaceous carcinoma, and therefore, their evidence does not exclude this diagnosis.

BACKGROUND Hormonal changes in pregnancy are known to alter melanocytic lesions, with some nevi noted to have increased mitotic figures and increased Ki-67 proliferation index. Additionally, cytomorphologic changes have also been noted, referred to as superficial micronodules of pregnancy. These changes may alarm the pathologist for malignancy, particularly nevoid melanoma. Immunohistochemistry for p16 has been recently utilized to distinguish benign nevi from melanoma. We assessed the use of p16 immunohistochemistry for distinguishing melanocytic nevi of pregnant patients from nevoid melanomas. METHODS Fourteen nevomelanocytic lesions were obtained from pregnant or postpartum patients along with 20 nevoid melanomas for comparison. Immunohistochemistry with p16 was performed on each melanocytic lesion. The percentage of nuclear p16 staining of dermal melanocytes was grouped on a scale of 25% to 50%, and >50%. RESULTS The majority of nevi from pregnant patients (81%) showed staining of >5% for p16. In contrast, the majority of nevoid melanomas (65%) had staining of

Cutaneous metastases from an adenocarcinoma of the Ampulla of Vater are very rare, with only a few cases previously reported. We present here an additional case in a 57-year-old woman who complained of a painful growth on her frontal scalp that she had noticed 4 months earlier. Her medical history included an ampullary adenocarcinoma, which was diagnosed 4 years ago, excised through a Whipple procedure, and treated using chemotherapy and radiotherapy. The scalp biopsy showed a dermal and epidermotropic well-differentiated glandular neoplasm with abundant neutrophils within the luminae of the tumoral glands. The tumor failed to express p63 and cytokeratin 5/6, whereas it was intensively positive for CK7 and E-cadherin. CDX2 expression was weak and focal. The immunohistochemical expression of DNA mismatch-repair proteins (MSH2, MSH6, MLH1, and PMS2) was preserved. Despite oncological treatment, the patient developed multiple cutaneous metastases during the ensuing several months, and eventually died 6 years after her initial diagnosis with widespread metastases.

Pilomatrix (pilomatrical) carcinoma is a rare cutaneous adnexal tumor with matrical differentiation and recurrent and metastatic potential. Sarcomatoid pilomatrix carcinoma is a rare variant which shows a sarcomatoid component intermingling with the epithelial one. There are only 4 cases previously published. We present an additional case on the hand of a 78 year-old man which appeared as a 6 mm hyperkeratotic, focally ulcerated plaque. A shave biopsy demonstrated a dermal infiltrative neoplasm, composed of markedly atypical-appearing basaloid cells with focal necrotic/ghost cells, as well as an intimately associated population of atypical oval to spindle-shaped cells. Both the epithelial and the sarcomatoid components expressed cytokeratins (CKs) AE1/AE3, CK 5/6 and CAM 5.2, as well as beta-catenin and LEF-1. The tumor failed to express CK7, CK20, S100, thyroid transcription factor 1 (TTF1), CDX2, prostate-specific antigen (PSA) and CD34. The tumor was completely excised with Mohs surgery, and there has been no recurrence in the 8 months of follow-up to date.

Mucin deposition in Spitz nevus seems to be a very rare phenomenon, as there have only been 3 cases previously published. We report 6 additional cases, half of them in women, and half in men. The ages of the patients varied from 5 to 47 years (mean = 30.17). Sizes of the nevi varied from 3 to 6 mm. Four lesions were located on the extremities, whereas one was located on the trunk (there was no clinical information about the other). A vascular lesion was suspected in 2 cases. Excision with clear margins was achieved in all cases but one. So far, there have been no recurrences after follow-ups varying from 1 to 5 years. The biopsy showed a symmetrical melanocytic Spitz nevus in all cases. Three cases were compound, and 3 cases were junctional nevi. The epidermis was either acanthotic or hyperplastic in all cases, with no epidermal consumption. Kamino bodies were found in 4 cases. The deposit of mucin was moderate in 5 cases and mild in one case. Mucin was found in the stroma between the dermal melanocytes in cases of compound nevi and in the melanocytic nests of the junctional component.

Atypical fibroxanthomas (AFX) are rare cutaneous tumors, which typically present as a solitary ulcerated papule or nodule on sun-damaged skin. Despite malignant-appearing features on histology, AFX typically pursue a benign clinical course. In rare instances, AFX can form collision tumors with other lesions. However, to the best of our knowledge, AFX in collision with a nevus has never been previously reported. In this study, we describe such a lesion for its novelty and challenge in diagnosis, as this case was originally considered to be melanoma arising in a nevus. On histologic examination, there were 2 distinct populations of cells; one composed of markedly atypical and pleomorphic epithelioid and oval to spindled cells, consistent with AFX, and the other, a bland-appearing intradermal nevus with congenital features. The AFX population stained positive with smooth muscle actin, CD10, and CD68 and was negative for S100, SOX10, Melan-A, desmin, pancytokeratin, CK5/6, and p63. Deep to this was a second population of small, bland-appearing melanocytes in a broad, band-like distribution. This unusual collision tumor between AFX and an intradermal nevus highlights the important role immunohistochemistry plays in avoiding the misdiagnosis and potential overtreatment of benign or low-grade lesions, and in identifying potential mimickers.

Some poroid neoplasias are known to show apocrine differentiation (ie, differentiation toward the folliculosebaceous and the apocrine units). In this sense, it is somewhat surprising that the immunoexpression of androgen receptors (ARs) has not been investigated yet in poroid neoplasias. In this study, we examined the immunoexpression of ARs in 40 poroid neoplasms (8 porocarcinomas and 32 poromas). We found intense and diffuse immunoexpression of ARs in 1 porocarcinoma. In addition, 7 poromas and 2 porocarcinomas showed focal immunoexpression of ARs. Nine of these 10 positive cases were found in men. We conclude that poroid neoplasias express ARs in about 25% of the cases, but the expression is usually focal/weak. However, the expression of this marker is not incompatible with a diagnosis of poroid neoplasia.

Anaplastic large cell lymphoma (ALCL) is a CD30+ T-cell non-Hodgkin lymphoma with two main clinical presentations: primary cutaneous (pcALCL) and systemic (sALCL). While rare cases of myxoid sALCL have been reported, there are no previous cases of myxoid pcALCL reported. We present two unusual cases of pcALCL showing prominent collections of dermal mucin closely intermingling with the anaplastic lymphocytes. Patient 1 was a 30-year-old woman who presented with ulcerated nodules on her neck, abdomen, chest, and shoulders. A systemic lymphoma was excluded by physical examination, positron emission tomography and computed tomography (PET-CT) scan, as well as by bone marrow biopsy and flow cytometry studies. The patient was closely followed up for 10 months without evidence of systemic involvement. The biopsy showed diffuse infiltration of the dermis by a CD2+, CD30+, ALK-negative ALCL. Patient 2 was a 55-year-old woman who presented with a single nodule on her right arm. A systemic lymphoma was excluded by physical examination as well as by a PET-CT scan. The biopsy showed diffuse and dense lymphoid infiltration of the whole biopsy by a CD3+, CD4+, CD30+, ALK-negative ALCL. The atypical lymphocytes were intermingled with large amounts of dermal stromal mucin.

Although Gottron papules are a relevant feature of dermatomyositis, they are reported in very few papers in the literature, and the largest series on the subject includes 11 cases. We intend to study the main histopathologic features of Gottron papules in a series of 12 biopsies. We evaluated hematoxylin-eosin stains on all cases. We also performed histochemical stains to evaluate the dermal deposition of mucin. Finally, we studied the CD123 cell population in the inflammatory infiltrate by immunohistochemistry. We found that the epidermis was either acanthotic or hyperplastic in all cases. We found a dermal inflammatory infiltrate in all cases but one. Mucin deposition in the reticular dermis was an inconstant feature. Vacuolization of the basal layer was also a frequent finding. There was thickening of the base membrane on periodic acid-Schiff stains in all our cases. We identified CD123 cells in all cases but 2. Intraepidermal CD123 cells were also found in 8 cases. All cases but one showed lymphangiectasia in the upper part of the dermis, including the papillary and reticular dermis. In addition, collapsed lymphatics were evident underlying the dermal sclerosis. We conclude that Gottron papules show typical features of localized lymphedema.

Dermal non-neural granular cell tumor (NNGCT) was first described in 1991 as an S100-negative polypoid non-melanocytic tumor. Although originally introduced in the literature as a primary cutaneous tumor, it was later emphasized that such qualification could not be held until the line of differentiation was clarified. It was also demonstrated that not all cases were polypoid. In the current study we try to further characterize this entity by presenting 5 cases of NNGCT. As expected, not all of them were polypoid. The ages of the patients varied from 10 to 43 (mean age 22). They all were composed of S100-negative granular cells with variable atypia and mitotic figures. None of them recurred in follow-up of up to 12 years (mean 8.2 years). We found evidence of folliculocentricity in 4 cases (in 1 case, this feature could not be investigated because the biopsy was a small shave specimen), that is, tumors were always surrounding, embedding, or following a hair follicle. In some occasions, such features were better demonstrated by immunohistochemistry against the arrector pili muscle. Our cases showed intense immunoexpression of CD10 and CD68. We conclude that NNGCT is morphologically related to the hair follicle and we believe that it is a granular cell dermal root sheath fibroma.

Angiolymphoid hyperplasia with eosinophilia (ALHE) is a poorly understood benign vasculoproliferative disorder. Histopathologicaly, the lesions are composed of a dermal or subcutaneous proliferation of blood vessels of varying sizes with plump and bland endothelial cells, which often show vacuolization and protrusion of the cytoplasm into the lumen. The vascular proliferation is admixed with a diffuse inflammatory infiltrate composed of lymphocytes, eosinophils, and mast cells. Lymphoid follicles with germinal centers can sometimes be seen. Additionally, fibrosis is a common accompanying feature. Some clinical and histopathological variants of ALHE have already been described in the literature. In this report, we present three rare associations of ALHE that have not been previously described. Case 1 was a 73-year-old woman with a lesion on her right medial thigh. Examination showed ALHE admixed with a chronic lymphocytic leukemic (CLL) infiltrate. Case 2 was a 55-year-old woman with a lesion on her right anterior ankle, which was a syringocystademoma papilliferum coexisting with an ALHE. Case 3 was a 54-year-old man with a lesion on the left medial thigh, which showed overlapping features of IgG4-related disease associated with areas of ALHE. Given these multiple and diverse associations, it seems likely that ALHE may be a reactive rather than neoplastic process.

Benign cutaneous mixed tumor (chondroid syringoma) is the cutaneous counterpart of the benign mixed tumor (pleomorphic adenoma) of salivary glands, consisting of both epithelial and mesenchymal elements. The incidence of cutaneous mixed tumor is rare, composing

We present the case of a 43-year-old white man with a complex lesion at the base of the penis that combines features of both a poroma and a condyloma with human papillomavirus (HPV) infection, atypias, and focal ductal differentiation. It was a papillomatous lesion with epidermal hyperplasia, which mainly contained focally pigmented monotonous basaloid cells. Ductal lumina with cuticular cells were easily identified. Atypias were focally evidenced, with nuclear enlargement and hyperchromasia. Hypergranulosis and koilocytosis were also present. Immunohistochemical studies indicated p16 and p53 immunoexpression in the areas with cellular atypia and koilocytosis. Studies with in situ hybridization showed positivity for HPVs 16/18 and 31/33 in such areas, with a high rate of proliferation indicated by Ki-67. There was no positivity for HPV 6/11. Epithelial membrane antigen highlighted the ductal lumina, whereas there was no immunostaining for carcinoembryonic antigen.

Author(s): Shiu, Jessica; Thai, Megan; Elsensohn, Ashley N; Nguyen, Nathalie Q; Lin, Kelly Y; Cassarino, David S

Epidermal inclusion cyst (EIC) and syringoma are both benign lesions that are primarily asymptomatic and occur at various places on the body. Although both EIC and syringoma are common, their joint appearance has not been previously reported. These benign proliferations target different populations, and with differing clinical presentations. Syringomas tend to develop in young females as smaller multiple lesions, while EICs often present in older males as single or multiple variants that are typically larger in size. They also possess distinctive histopathological appearances that can used for their diagnosis. Furthermore, despite both having unclear etiologies, the involvement of the eccrine duct has been a proposed mechanism in the development of both lesions. Thus, further investigation of eccrine ducts in the pathology of these lesions can be the basis for assessing the association between EICs and syringomas. We report a unique case of a 16-year-old boy who presented to the clinic with multiple cysts (at least 20) on the scrotum, most of which consisted of both EIC and syringoma histologically. We are not aware of any previous reports of patients with multiple combined syringomas and EICs, and their potential association should be further explored.

Lymphomatoid papulosis (LyP) is classified as a CD30+ primary cutaneous lymphoproliferative disease. The phenotypic variability along the spectrum of CD30+ lymphoproliferative diseases is highlighted by the distinct histologic subtypes of LyP types A, B, C, and the more recently described types D, E, and F. We report the case of an elderly woman with a clinical presentation and histopathologic findings consistent with LyP, whose atypical CD30+ infiltrate uniquely demonstrated a spindle-cell morphology. To our knowledge, this is the first reported case of LyP characterized by CD30+ spindle-shaped cells, and may represent a new and distinct histologic variant of LyP.

Interdigitating dendritic cell sarcoma (IDCS) is a rare tumor of spindle to ovoid cells intermixed with lymphocytes and plasma cells. Primary cutaneous IDCS, with no nodal or other organ involvement is extremely rare, with less than 10 cases reported to date. Herein, the authors describe a case in which a 61-year-old man presented with scattered subcutaneous nodules on his left shoulder and right anterior thigh. A biopsy was performed, and the histopathologic findings revealed prominent, diffuse superficial, and deep dermal infiltration by an atypical epithelioid-shaped tumor forming sheets and cords infiltrating throughout the dermis. Immunohistochemical stains were strongly and diffusely positive for S100, CD45, CD68, and lysozyme, whereas CD21, CD23, CD3, CD20, CD30, CD34, and CD117 were all negative. The histologic and immunohistochemical findings were consistent with an IDCS. A positron emission tomography scan was negative for metastases, leading to the diagnosis of primary cutaneous IDCS. The patient was started on chemotherapy with gemcitabine and docetaxel, and was stable at 4 months follow-up. Our findings contribute to the limited existing literature on primary cutaneous IDCS. This is the first documented case in which chemotherapy with gemcitabine and docetaxel was implemented for treatment, helping to establish an optimal treatment protocol for clinical remission.

Atypical fibroxanthoma (AFX) is a group of cutaneous tumors characterized by a population of fusiform, epithelioid and pleomorphic cells. Clinically, AFX is commonly found on the head and neck of older adults as a solitary ulcerated nodule. Clear cell atypical fibroxanthoma is a very rare variant of AFX, with only 13 cases reported to date. The differential diagnoses often include dermal neoplasms composed of clear cells, such as squamous cell carcinoma, basal cell carcinoma, metastatic renal cell carcinoma and balloon cell malignant melanoma. These diagnoses can be ruled out by the typical immunohistochemical profile of clear cell AFX, which is negative for specific epithelial and melanocytic markers. Herein, we describe a rare and unusual case of clear cell AFX arising on the ear of a relatively young adult patient. Histologically, the dermis was completely replaced by an atypical population of vacuolated cells with numerous atypical mitoses. Immunohistochemical stains were negative forpancytokeratin, CK5/6, CK7, and p63 S100 and Melan-A stains. CD10 and CD68 stains were positive, making the findings consistent with the diagnosis of clear cell atypical fibroxanthoma.

Sarcomatoid carcinomas are rare malignant tumors, which usually demonstrate a well-differentiated epithelial component in association with a poorly differentiated spindle-cell component. Several different subtypes have been reported and categorized primarily under the differentiated epithelial component, with the majority of cutaneous sarcomatoid carcinomas arising in the setting of a basal cell or squamous cell carcinoma. To date, only 4 cases of sarcomatoid porocarcinoma have been reported in the literature. The authors present a case of an 84-year-old woman with an ulcerated papule on her scalp for several months. Histopathology revealed an exophytic and endophytic epidermal proliferation with multiple mitoses and ductal differentiation overlying a poorly differentiated, infiltrative spindle-cell proliferation in the dermis. Ductal and cystic structures were scattered throughout the malignancy. Immunohistochemistry was notable for strong and diffuse pancytokeratin positivity, p63 positivity, focally positive carcinoembryonic antigen within the ductal lumina, and periodic acid-schiff-positive, diastase-resistant intracellular deposits. They present the findings of this rare case of primary cutaneous sarcomatoid porocarcinoma.