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This review considers neoplastic lesions that originate in the skin, and which have the potential to imitate hematopoietic proliferations at a histological level. They include lymphoepithelioma-like carcinoma, Merkel cell carcinoma, benign lymphadenoma, pseudolymphomatous angiosarcoma, lymphadenoid dermatofibroma, lymphomatoid atypical fibroxanthoma, histiocytoid (epithelioid) hemangioma, and inflamed melanocytic lesions. The clinical and pathological features of those tumors are considered., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The head and neck area has disproportionate number of cutaneous tumors given the surface area, as compared with the rest of the body. Many of the tumors are related to chronic actinic damage and the most common by far are squamous and basal cell carcinomas. Atypical fibroxanthoma refers to a group of usually indolent cutaneous tumors that occur in older adults and are characterized histologically by a population of fusiform, epithelioid, and pleomorphic cells, numerous cells in mitosis, and intracytoplasmic lipidization in some cells. Numerous histologic variants have been described, including a clear-cell, desmoplastic or keloidal, granular, angiomatoid, hemosiderotic, and myxoid, among others. These tumors have a mesenchymal immunophenotype. Some authors believe that atypical fibroxanthoma is a dedifferentiated variant of squamous cell carcinoma. We present a review of this particular neoplasm with special emphasis on the histomorphology, subtypes, immunophenotypic profile, and discussion of differential diagnosis., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Lipomas are the most common subtype of benign soft tissue neoplasms and can occur anywhere in the body. Differentiation into a diversity of mesenchymal elements, such as blood vessels, fibrous tissue or muscle, is a frequent event. However, the presence of bone or cartilage in these tumors is extraordinarily rare with very few cases reported in the head and neck area. We report a case of an 'osteochondrolipoma' of the chest wall, in a young individual, providing a rationale in support of this as a possible and distinctive histologic subtype of lipomas, as well as discussion in the differential diagnosis of this lesion., (Copyright © 2011 John Wiley & Sons A/S.)

Currently, the treatment of choice for refractory tertiary hyperparathyroidism is a total parathyroidectomy with autotransplantation of the parathyroid tissue into the forearm. Recurrent hyperparathyroidism after autotransplantation requiring surgical excision of the autograft is uncommon. We describe a female patient with recurrent hyperplasia who underwent an excision of her parathyroid autograft. The excisional specimen was submitted to pathology with the only provided history of a 'left arm mass'. The lack of clinical history led to a preliminary impression of an adnexal neoplasm by the primary pathologist., (Copyright © 2009 John Wiley & Sons A/S.)

Background: Lipodermatosclerosis is a chronic fibrosing process that involves both lower legs and classically affects Caucasian women in their 60s., Objective: The objective is to define the histologic spectrum seen this condition., Methods: A total of 25 cases were collected prospectively and all were stained with hematoxylin-eosin, von Kossa, and Verhoeff-van Gieson., Results: Patient age ranged from 33 to 84 years (mean age 62.6 years). The female to male ratio was approximately 12 to 1. All lesions were present on the lower extremities, between the knee and ankle. Lesion duration ranged from 2 months to 2 years (mean 9.5 months). Clinically, the lesions were erythematous, tender, indurated plaques or nodules. The characteristic histologic findings were seen almost exclusively in the subcutaneous tissue, involving primarily the lobules but also the septa. Adipose changes included micropseudocyst and macropseudocyst formation, necrotic adipocytes, lipomembranous change, and lipogranulomas with xanthomatous macrophages. The lesions were largely devoid of dermal, septal, or lobular neutrophilic or lymphocytic inflammation. Medium vessel calcification was seen in 13 cases. The accumulation of basophilic elastic fibers located deep in the septa was present in all the cases. These fibers had a moth-eaten appearance and resembled pseudoxanthoma elasticum. In 21 of 25 cases, these fibers were positive with both the von Kossa and Verhoeff-van Gieson stains., Limitations: The cases in the series were not compared with age-, sex-, and location-matched biopsy specimens or biopsy specimens of other fibrosing conditions., Conclusion: This constellation of histologic changes is diagnostic of lipodermatosclerosis. The presence of pseudoxanthoma elasticum-like changes is a helpful, but not unequivocal, clue in this condition., (Copyright 2009 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

We report an unusual histopathological variant of a glomus tumor that arose in a peculiar topographic site, a sclerotic glomus tumor. Unlike conventional glomus tumors or glomangiomas that have a loose fibrous stroma with variable hyaline and myxoid changes, the case reported herein had a diffuse, hyalinized, sclerotic stroma. A further difference was that the majority of glomus tumors and glomangiomas occur in the subungual area, trunk, or extremities, whereas the present tumor occurred on the ear. Due to the peculiar histological features and location, other tumors were considered in the differential diagnosis to include Merkel cell carcinoma, primitive neuroectodermal tumor, and small cell melanoma. This article illustrates a unique variant of a glomus tumor, which to our knowledge has not been previously described.

Cornoid lamellation is a specific disorder of epidermal maturation manifested by a vertical "column" of parakeratosis and is the hallmark of porokeratosis. The cornoid lamella is characterized by a ridgelike parakeratosis. We present 11 patients with solitary lesions of a distinct pattern of cornoid lamellation. The mean age at presentation clinically was 57 years; there were 9 men and 2 women. The duration of the lesions ranged from 3 months to 5 years (mean of 23 mo). All lesions were solitary, distributed mainly on the distal upper and lower limbs, and were clinically described as hyperkeratotic plaques or nodules; some were verrucous. Histologic examination showed a well-defined lesion characterized by acanthosis and verrucous hyperplasia with prominent multiple and confluent cornoid lamellae. No additional lesions were identified in any patient, with a mean follow-up duration of 34 months. No personal or family history of porokeratosis was elicited and no immunosuppressive conditions were noted. These lesions with multiple and confluent cornoid lamellae represent benign acanthomas with features of porokeratosis. As a solitary tumorlike lesion, it is akin to warty dyskeratoma and epidermolytic acanthoma, thus we have coined the term porokeratoma.

Background: Circumscribed acral hypokeratosis (CAH) is an idiopathic condition that typically presents as an acquired, solitary, asymptomatic, well-defined, depressed, flat-based deformity, with a slightly raised border on the palm or, rarely, the sole. Histologically, the lesional epidermis is depressed with a characteristic, abrupt, hyperkeratotic, slightly-raised ridge at the transition from normal skin., Objective: We sought to present 3 additional cases of CAH., Methods: A review of 3 cases of CAH was performed. Liquid phase polymerase chain reaction (PCR) was conducted to evaluate for human papillomavirus (HPV)., Results: Three cases of CAH were reviewed. One patient had a history of a burn at the site prior to developing the disorder while another patient, as a child, had a history of verruca plantaris in the same location. Lesions were solitary, involving the palm or sole, in 2 cases and in one case they were multiple involving both the palms and the soles. HPV testing detected HPV type 6 in the lesion of one patient who previously was treated for warts in the same location. Topical fluorouracil, calcipotriol ointment under occlusion, and clobetasol ointment under occlusion were unsuccessful in one patient., Limitations: In case 2, we were pathology consultants and unable to evaluate the clinical appearance of the lesion., Conclusions: CAH may involve palms and/or soles. Lesions may be solitary or multiple, and vary widely in size. We believe that CAH most likely represents a reaction pattern developing in response to various stimuli, including trauma, HPV, or both.

Presented herein are 18 cases of erythematous, scaly papules or plaques with microscopic features of both seborrheic keratosis and psoriasis. There was, however, no known clinical diagnosis of psoriasis in any patient, neither at initial presentation nor on follow-up examination. Most lesions were solitary, present for 6-7 months, and identified on the upper or lower extremities. Other sites included the scalp, neck, shoulders, and back. Men were affected slightly more often than women. The mean age at diagnosis was 66.8 years. The most common diagnoses, clinically, were seborrheic keratosis, followed by basal cell carcinoma, Bowen's disease, actinic (solar) keratosis, and squamous cell carcinoma, among others. The lesions averaged less than a centimeter in diameter and were dome shaped, scaly, and yellow to gray-tan. Histologic examination revealed irregular verrucous epidermal acanthosis, with hyperkeratosis, parakeratosis, hypergranulosis, and intracorneal collections of neutrophils, often in alternating tiers. Vascular dilatation and lymphocytic chronic inflammation were present in the superficial dermis. Periodic acid-Schiff (PAS) stain for yeasts or dermatophytes was negative in all cases. There was no clinical evidence of disseminated psoriasis in any patient; the mean follow-up duration was 22.6 months. We have coined the term psoriasiform keratosis as a provisional appellation until the nature of these lesions is determined more definitively. It is unclear whether a psoriasiform keratosis is a rudimentary manifestation of psoriasis or a lesion sui generis.

We report on two patients with granular cell atypical fibroxanthoma. Both neoplasms were solitary, light-tan, dome-shaped papules on sun-exposed areas of the head in two elderly white men. Microscopically, these neoplasms showed a dermal proliferation of pleomorphic granular cells with irregular hyperchromatic nuclei, multinucleated cells, and scattered mitoses. Immunohistochemical stains were positive for CD68 and vimentin and negative for Melan-A or human melanoma black (HMB)-45, S-100 protein, pancytokeratin, and actin, consistent with atypical fibroxanthoma. The differential diagnosis of granular cells in neoplasms containing cytological pleomorphism is challenging in view of the many different neoplasms that may present with granular cytoplasm. These include the conventional granular cell tumor and its malignant form, leiomyoma, leiomyosarcoma, dermatofibroma, dermatofibrosarcoma protuberans, and angiosarcoma.

Cutaneous vascular proliferations are a vast and complex spectrum. Many appear as hamartomas in infancy; others are acquired neoplasms. Some vascular proliferations are hyperplastic in nature, although they mimic hemangiomas, i.e., neoplasms. The vast majority of the vascular lesions are hemangiomas. Between the hemangiomas and frankly angiosarcomas, there is a group of neoplasms that are angiosarcomas, albeit ones of low grade histologically and, probably, biologically. The term "hemangioendothelioma" has been created to encompass these neoplasms. Vascular proliferations are, fundamentally, composed of endothelial cells. Some hemangiomas, however, contain also abundant pericytic, smooth muscle, or interstitial components, or a combination of them. These heterogeneous cellular components are present usually in hemangiomas. Some of the newly described vascular proliferations, however, are difficult to differentiate from some of the angiosarcomas. Others are markers, occasionally, of serious conditions such as Fabry's Disease (angiokeratoma) and POEM's syndrome (glomeruloid hemangioma). Kaposi's sarcoma continues to be an enigma. The demonstration of Herpes virus 8 in this condition raises doubt about its neoplastic nature. The demonstration of endothelial differentiation of its nodular lesions is tenuous and its true nature remains unresolved. While physicians have known about post-mastectomy angiosarcomas from the origin of the radical mastectomy, a new group of unusual vascular proliferations of the mammary skin are being defined. These lesions arise in the setting of breast-conserving surgical treatment with adjuvant radiation therapy. The incubation period is usually 3 to 5 years, in contrast with the 10, or more, in classical cases of post-mastectomy angiosarcoma. These lesions usually are subtle, both clinically and histologically, in contrast with the "classical," dramatic presentation of mammary angiosarcoma. The spectrum of findings ranges from "simple" lymphangiectasia-like vascular proliferations to unequivocal angiosarcomas. The pathogenesis of these lesions remains a mystery. There are very few clues that allow one to separate hemangiomas from angiosarcomas. The presence of heterologous cellular elements and, particularly, well-developed smooth muscle components tends to favor a hemangioma. Similarly, the presence of thrombosis usually supports hemangioma. Nevertheless, there are no unequivocal or reliable individual diagnostic criteria. A thorough knowledge of the different conditions and their differential diagnoses eventually leads to the proper diagnosis in most cases.

Tubulopapillary hidradenoma is a benign sweat gland tumor that appears as a well-defined, superficially located dermal nodule. It combines ductal as well as apocrine and eccrine glandular differentiation. Microscopically, the tumor is composed of tubular structures that characteristically show intraluminal non-villous papillary projections and a peripheral myoepithelial cell layer. A tumor that is histologically and immunohistochemically identical to tubulopapillary hidradenoma occurred in the mandible of a 73-year-old man and resulted in considerable diagnostic difficulty. The neoplasm developed in a mandibular cyst and recurred 5 years after initial enucleation. This is the first report of a central (intraosseous) sweat gland adenoma of the mandible. The differential diagnosis and possible histogenesis are discussed.

We have previously shown that human metallopanstimulin (MPS-1) is a ubiquitous 9.4-kDa multifunctional ribosomal S27/nuclear "zinc finger" protein which is expressed at high levels in a wide variety of cultured proliferating cells and tumor tissues, including melanoma. In the present study, we have examined the expression of the MPS-1 protein in various types of human benign and malignant melanocytic lesions of the skin. The expression of the MPS-1 protein was studied by immunohistochemistry using specific anti-MPS-1 antibodies. We found that in benign nevi, the staining is weak and in a gradient; most often, only type A melanocytes stain positive. The B and particularly the C types are negative. Remarkably, congenital nevi show a similar gradient staining of regular benign nevi, but in addition one example showed intensely positive dermal nodules adjacent to areas of negative melanocytes. In melanomas, the staining patterns for MPS-1 are more complex. While some melanomas stain evenly and intensely positive, others have remarkably variable expression of MPS-1. The scattered melanocytes migrating to the upper layers of the epidermis are usually intensely positive. In summary, benign lesions stain in an orderly pattern with staining gradients that correlate with the cellular differentiation of the nevi. Malignant melanomas have an erratic, often intense staining that also correlates with the disorderly growth of these neoplasms. These differential results indicate that the MPS-1 antigen is a useful marker for melanocytic lesions at the immunohistochemical level.

Introduction: Adenolipoma of the skin is an unusual microscopic variant of the solitary lipoma, superposable to the adenolipoma of the breast, characterized by the presence of normal eccrine sweat glands inside the fat proliferation., Observations: Two new cases are reported., Discussion: Adenolipoma of the skin is a benign lesion whose clinical features are similar to those of solitary lipoma. Probably, it is only a histological curiosity in which the eccrine glands are entrapped and carried by the adipose proliferation.

Histologic evaluation for alopecia can be difficult and in part can be attributed to confusing categorization and limited information derived from examination of traditionally prepared biopsy specimens. The transverse section technique has many advantages, and with experience is the preferable method for evaluating specimens for alopecia. Using this technique, numerous follicles can easily be seen in one tissue profile allowing evaluation of follicular density, follicular unit morphology, and follicular growth dynamics, ie, anagen-telogen ratio. Specimens are categorized as scarring or nonscarring alopecia, and further diagnostic criteria discussed herein assist the pathologist in making specific diagnoses of nonscarring and scarring alopecias. Scarring alopecia may be primary or secondary, and primary scarring alopecias are further classified as lymphocyte-associated and neutrophil-associated. Although the clinical impression is very important in diagnosing alopecia, transversely sectioned biopsy specimens can greatly aid the diagnosis and management of patients with alopecia.

Epithelioid cell histiocytoma is a recently recognized lesion that is considered to be a variant of cutaneous fibrous histiocytoma (dermatofibroma). Ten cases are presented, including their light microscopic, immunohistochemical, and ultrastructural features. Eight of the cases are similar to those previously reported, presenting as elevated nodules arising on the extremities and composed of epithelioid histiocytes with overlying epidermal effacement. Two of the cases were composed of cells with the same morphologic and immunohistochemical characteristics as typical epithelioid cell histiocytoma, including factor XIIIa positivity, but these arose in the reticular dermis and exhibited prominent cellularity.

The majority of cutaneous angiosarcomas display typical architectural features of irregular anastomosing vascular channels in the dermis and subcutis. Nuclei are usually hyperchromatic and pleomorphic but the volume of cytoplasm of the neoplastic cells is often small. Diagnosis can be made readily on an adequate biopsy. We recently experienced difficulty diagnosing an angiosarcoma composed predominantly of cells with abundant granular cytoplasm. We were able to compare the present case with sections obtained from the only other reported example. The architectural expression of an anastomosing vascular pattern in areas of tumor, combined with the positive staining for Factor VIII-related antigen (FVIIIRAg) and Ulex europaeus agglutinin-1 (UEA1) enabled us to make a diagnosis of angiosarcoma. The tumor failed to stain for the other endothelial markers (CD31 and CD34) which were positive in the original case. A marker for lysosomes (CD68) stained the granules in both cases. The granular cell variant of cutaneous angiosarcoma is very rare. Diagnosis is possible by recognizing the typical anastomosing neoplastic vascular channels at the periphery of the lesion, and by use of a combination of lectin (UEA1) and immunohistochemical (FVIIIRAg, CD34 and CD31) endothelial markers.

Clear cell basal cell carcinoma (BCC) is an unusual variant of BCC which is characterized by a variable component of large clear cells. Twenty cases are presented which are further subdivided into pure, mixed, or metatypical categories. Although initially thought to represent sebaceous or tricholemmal differentiation, electron microscopic studies demonstrated that the clear cell changes are a degenerative phenomenon, probably involving lysosomes.

Background: We have identified nine cases of a variant of superficial lipoma that are characterized by the presence of eccrine sweat glands., Objective: The purpose of this study was to elucidate the clinical and histopathologic features of this distinctive lesion., Methods: Nine cases of lipoma that contain eccrine glands were retrieved from our pathology files from 1989 through 1992. Their clinical and histopathologic features were studied and compared with those of conventional lipoma., Results: The clinical features of these lesions did not deviate appreciably from those of the usual lipomas. However, their microscopic appearances differed by the presence of displaced and distorted eccrine glands. One lesion had the added features of a myxolipoma., Conclusion: Adenolipoma of the skin is a distinct lesion that can occur in the dermis or subcutaneous tissue.

Background: Angioendotheliomatosis has recently been separated into two types. Malignant angioendotheliomatosis is a lymphoma in which the neoplastic cells accumulate in vascular lumens. Reactive angioendotheliomatosis is a proliferation of capillaries that is less well characterized., Objective: Our purpose was to describe the clinical and histopathologic features of three cases of reactive angiomatosis in patients with cryoproteinemia., Methods: Clinical and histologic data were correlated. Immunoperoxidase staining and electron microscopy were used in the histologic evaluation., Results: All three cases showed tufts of capillaries with luminal deposits of cryoproteins. Immunohistochemical studies showed that the cellularity of the tufts was primarily caused by a proliferation of pericytes., Conclusion: Cryoproteinemia can cause angiomatosis that simulates a vascular neoplasm.

Six cases of a distinct, histologically anaplastic variant of mammary Paget's disease are described. Patients ranged in age from 40 to 85 years. All patients had scaling erythematous lesions confined to the nipple; none had palpable breast masses. Histologically, the lesions had features resembling Bowen's disease, including full-thickness epidermal atypia, loss of nuclear polarity, and marked cytologic anaplasia. Intraepidermal acantholysis was a distinctive feature in all cases. In some biopsies, small groups and single typical Pagetoid cells were seen within the areas of confluent Bowen-like change. Immunohistochemically, carcinoembryonic antigen (CEA) was positive in three of six patients; epithelial membrane antigen (EMA) in five of six patients, and cytokeratin AE1/AE3 in three of six patients. Mucicarmine stains were uniformly negative. In our series, anaplastic Paget's disease was associated with concomitant invasive ductal carcinoma in three of six patients (50%). This percentage is significantly higher than that previously reported for patients with Paget's disease and without palpable breast mass. Histologic features that are helpful in distinguishing between anaplastic Paget's disease and Bowen's include cleft-like acantholysis, absence of dyskeratotic cells, and persistence of basal cell layer. More rarely, but very helpful when present, are underlying ductal carcinoma, intracellular lumina, and associated conventional Paget's disease. Immunohistochemistry results were variable and of relative value. Our study suggests that a nipple lesion histologically resembling Bowen's disease is likely to represent anaplastic Paget's disease.

Eight cases of apocrine (tubular branching lumina) type cutaneous mixed tumors with follicular and sebaceous differentiation are presented. All eight tumors arose on facial skin; six patients were male and two were female. The lesions showed a cystic or nodular clinical appearance and were surgically excised. Histopathological examination confirmed the diagnosis of apocrine type of cutaneous mixed tumor in each case. Follicular differentiation consisted of (a) keratinous cysts with infundibular keratinization (infundibular differentiation); (b) hair bulbs with papillary mesenchyma, matricial differentiation with basophilic, transitional, and shadow cells, trichohyaline granules, vellous hair shafts, and clear cells of the outer root sheath (anagen differentiation); and (c) epithelial columns composed of inner cells with plump oval nuclei and scant cytoplasm, and similar cells at the periphery that were arranged in a palisade, resembling the inferior segment of a normal hair follicle in telogen. Sebaceous differentiation was represented by mature sebaceous cells, either as single cells or as small islands, within epithelial tracts of the tumor. The proportion of the areas showing these different types of differentiation varied among lesions, but some follicular differentiation was always present, whereas three cases lacked sebaceous differentiation. Immunohistochemical analysis in three cases with respect to their eccrine or apocrine differentiation showed contradictory results as in a previously reported series of cutaneous mixed tumors. The presence of follicular and sebaceous differentiation in the apocrine (tubular branching lumina) type of cutaneous mixed tumor is a confirmation of the apocrine nature of this neoplasm as well as an expression of the common embryologic derivation of all elements of the folliculosebaceous-apocrine unit.

We describe two patients with crusted perineal plaques that were biopsied and diagnosed as Paget's disease. Resection specimens of each contained a dermal mucinous carcinoma with extensive epidermotropism and coexistent epidermal basaloid proliferations closely resembling fibroepithelioma (Pinkus). The presence of the Paget phenomenon was supported by histochemical, immunohistochemical, and ultrastructural evidence. No other primary neoplasms were found in either patient. Followup at 2 1/2 and 3 1/2 years, respectively, has been negative. We conclude that either the fibroepitheliomatous changes may be induced by or may represent a collison (unlikely) with the epidermotropic mucinous carcinoma. It is proposed that the concept fibroepitheliomatous Paget phenomenon be used to stand for the histologic changes common to our cases as well as those previously reported.

In recent years, the classification of vascular lesions has been expanded and modified with the addition of several newly described entities, the redefinition of others, the recognition of lesions of borderline biologic behavior, and the need to avoid misdiagnosis with early Kaposi's sarcoma. This review clarifies the nomenclature, updates information on previously known lesions, and summarizes data on several recently discovered, lesser-known entities such as glomeruloid hemangioma, microvenular hemangioma, and multinucleate cell angiohistiocytoma. Clinicopathologic features and differential diagnosis are emphasized.

Ten examples of a distinctive vascular tumor are reported. These benign acquired lesions typically occur as small, enlarging lesions that favor the extremities, particularly the forearms, of young to middle-aged adults. Clinically, they are purple to red lesions generally thought to be hemangiomas. Histologically, there is a pattern of irregular, branching venules with inconspicuous lumina and lack of cellular atypia. Because the lesions do not conform to existing classifications of vascular tumors, they have been designated with the histologically descriptive name of microvenular hemangioma. Although speculative, they are felt to represent a form of acquired venous hemangioma.

Thirteen cases of a unique cutaneous tumor are presented. The lesions presented as single, nondescript, skin-color nodules. Eleven were located on the head and two were on the legs. The male/female ratio was 8:5. The age at diagnosis ranged between 21 and 55 years (mean: 39). The duration of the lesions was from several months to more than 20 years. All tumors were excised and did not recur. The tumors typically presented as well-circumscribed nodules with scant or no epidermal connections. (One example, however, had a plate-like configuration amply connected with the basal layers of the epidermis.) The proliferation consisted of multiple, rounded lobules of basaloid cells with some degree of peripheral palisading, immersed in a dense, fibrous stroma. There was an intense infiltrate of small lymphocytes within the lobules, with some spillage into the stroma. No clear adnexal differentiation was noted except for rare isolated cells showing apparent sebaceous differentiation within the tumor lobules. Areas of central keratinization were also present. Numerous cells with ample amphophilic cytoplasm, large vesicular nuclei, and prominent nucleoli were also seen. Immunohistochemistry confirmed the presence of keratin within tumor cells. Common leukocytic antigen highlighted the intense intralobular lymphocytic component. Vimentin not only highlighted the stromal fibroblastic component, but also stained scattered intralobular cells. Epithelial membrane antigen was positive within some of the large intraepithelial cells. S-100 protein was extensively positive within dendritic intralobular and stromal cells. Lymphocytic markers demonstrated a polyclonal B and T population. This unique tumor appears to represent a form of adnexal neoplasm with basaloid features, possibly immature pilosebaceous differentiation.

Juvenile xanthogranuloma occurring in soft tissue is rare and has received little attention. This report describes cases of deep juvenile xanthogranuloma occurring in the soft tissues of three children. Each tumor was a solitary lesion that arose, respectively, in the superficial skeletal muscles of an 8-month-old girl, the subcutis of the scalp of a 3-month-old boy, and the subcutis of the forehead of a 10-year-old girl. Two lesions were grossly firm, tan-yellow, and homogeneous. Histologically, the subcutaneous lesions were relatively circumscribed; the third lesion infiltrated muscle and contained widely separated skeletal muscle fibers. All lesions showed sheets of uniform amphophilic or acidophilic cells with occasional eosinophils and rare Touton giant cells. In two cases and in cutaneous controls, positive immunoperoxidase stains (HAM-56, HHF-35, and vimentin) supported macrophagic-myofibroblastic differentiation. S-100 protein, MAC-387, and factor XIIIa were negative. Electron microscopy in one case also supported macrophagic-myofibroblastic differentiation. Langerhans granules were absent. Follow-up of 7, 6, and 5 years indicated no recurrences. The differential diagnosis includes deep fibrous histiocytoma and cellular subcutaneous neural tumors.

A cutaneous mastocytoma with associated histologic features of eosinophilic cellulitis is reported. The tumor occurred as a small, asymptomatic lesion on the left thigh of a 4-year-old boy. Microscopically, an accumulation of mast cells, microgranulomas, eosinophils and 'flame figures' was present. A pathogenesis involving mast cell degranulation, eosinophil chemotactic factors and eosinophil major basic protein is discussed.

Four cases of large eccrine acrospiroma (three benign, one malignant) are reported. The benign tumors involved the lower extremities of two women and one man (73 to 89 years of age). The duration of the lesions ranged from 10 to 20 years. The malignant tumor involved the left side of the chest of a 60-year-old man. Its occurrence in a lesion that had been present for 40 years suggested malignant transformation of a pre-existing benign eccrine acrospiroma. Each tumor showed little to no cellular atypia. Mitotic rates (mitotic figures per 10 high-power fields) varied both between and within lesions. Average mitotic rates did not differentiate the benign from the malignant tumors. The most important distinguishing features of large benign eccrine acrospiromas are the relative circumscription, the lack of cellular atypia, and the absence of stromal, perineurial, and angiolymphatic invasion.

This report describes four cases of a previously undocumented circumscribed idiopathic inflammatory fibrosclerotic lesion of the skin. The lesions occurred in two black women and two white men; they had been apparent from months to a year. The nodules were solitary; two were located on the arm, one on the calf, and one on the posterior neck. The clinical diagnoses included nodules, keratinous cyst, pilar tumor, pilomatricoma, vascular leiomyoma, dermatofibroma, and metastatic carcinoma. The lesions were grossly white, homogeneous, and circumscribed; one was located in the superficial subcutis and three in the reticular dermis. Histologically, they were sharply circumscribed and surrounded by a dense peripheral rim of lymphocytes and plasma cells. Peripheral germinal centers were noted in two cases. All cases had variable amounts of fibrosis centrally, giving them the low-power appearance of lymph nodes; however, no subcapsular or medullary sinuses were found. In the center of the lesions, the mononuclear infiltrate was accompanied by eosinophils and neutrophils. Virtually imperceptible vasculature was noted in portions of three lesions; in the fourth lesion, high endothelial venules were seen in the lymphoid portions, and "targetoid" perivascular sclerosis was seen in the central portions. There appears to be a transition from the early, mostly inflammatory, lesions to the sclerotic ones. The process seems to be reactive in nature. No obvious local or systemic etiology was found in our series, and follow-up of 2 to 5 years has been noncontributory. These mixed-cell proliferations resemble the extracutaneous masses that have been described in numerous viscera--particularly the lung--as "inflammatory pseudotumors" or "plasma cell granulomas." In our opinion, these lesions also bore a superficial resemblance to cutaneous lymphoid hyperplasia secondary to insect bites. Other differential diagnostic considerations include dermatofibroma, nodular fasciitis, Kimura's disease, epithelioid (histiocytoid) hemangioma, and reactive lymph nodes.

A 63-year-old woman with fibrous histiocytomas showed cholesterol deposition in the setting of type IIB hyperlipidemia. The two lesions involved the left leg and right thigh. One had typical features of a fibrous histiocytoma including changes of the overlying epidermis. The other was essentially replaced by cholesterol deposits and could not be differentiated from a tuberous xanthoma. This case illustrates the histiocytic response of fibrous histiocytomas to a hyperlipoproteinemic microenvironment.

A clinical and histologic review of 22 patients (13 males, 9 females) with cutaneous lesions classified as desmoplastic trichilemmoma is reported. Typically, the lesions occur as solitary dome-shaped papules on the face during (at least) the fifth decade of life. The average age was 64 years (range 19-89) with a median age of 66.5 years. The most frequent clinical diagnosis was basal cell carcinoma, and the most common sites were the lip, eyebrow and nose. Two lesions occurred in examples of nevus sebaceus of Jaddasohn. The proportion of desmoplasia varies, but is generally between 20% to 60% of the lesion. Ulceration is seen in a minority of lesions but when present, is closely associated with underlying desmoplasia. Desmoplasia may be seen in small, as well as large, trichilemmomas; it generally occurs centrally but at times may be seen peripherally. The appearance of strands of epithelial cells entrapped in dense fibrosis and hyalinization may mimic desmoplastic variants of squamous cell carcinoma and basal cell carcinoma. This appearance may be particularly troublesome when the desmoplasia occurs at the base of the biopsy specimen. Knowledge of this phenomenon and the search for more typical features of trichilemmoma such as clear cells and peripherally palisaded columnar cells upon a thickened, eosinophilic basement membrane will allow the correct diagnosis to be made. We believe that the desmoplasia occurs as a secondary change in pre-existing trichilemmomas.

Three examples of cellular angiolipoma are presented. They occurred as part of multiple, occasionally painful, subcutaneous nodules on the extremities and trunk of healthy men. There was no familial tendency. Grossly, the cellular angiolipomas were small lesions, approximately 1 cm. Histologically, dense cellular angiomatous tissue comprised more than 95% of the lesions. Much of this component contained prominent spindle cells. Lesser degrees of involvement in the other subcutaneous nodules illustrated the continuum of histology between cellular angiolipomas and more typical angiolipomas. The differential diagnosis of cellular angiolipomas includes spindle cell lipoma, Kaposi's sarcoma, and other vascular tumors. The most important distinguishing features are encapsulation, intravascular fibrin thrombi, septation, association with other more typical angiolipomas, and occurrence in healthy individuals.