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Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma, primary cutaneous CD30 lymphoproliferative disorders (pc CD30 LPD) being the second most prevalent. There is evidence that MF and pc CD30 LPD may coexist and share T-cell clonality, suggesting a common origin. These findings were supported by a T-cell receptor clonality assessment by the polymerase chain reaction coupled with capillary electrophoresis, although results produced by this method may be ambiguous. We describe an otherwise healthy 46-year-old man who developed, over the course of 5 months, a tumor consisting of primary cutaneous anaplastic large cell lymphoma and, subsequently, several papules of lymphomatoid papulosis (LyP). Both lymphomas appeared on a single patch of MF, which had been present on the patient's right buttock for at least 2 years. T-cell receptor clonality of the 3 types of neoplastic lesions and apparently non-involved skin were assessed by a next-generation sequencing-based method. We found that MF, primary cutaneous anaplastic large cell lymphoma and LyP harbored the same top 2 clones. Non-involved skin harbored other T-cell clones. In this patient, these findings suggest that MF, LyP and pc CD30 LPD were different clinicopathological manifestations arising from the neoplastic proliferation of the same T-cell clone.

Peripheral T-cell lymphoma (PTCL), not otherwise specified (NOS) is a diagnosis of exclusion, showing extreme cytological and phenotypic heterogeneity. Skin involvement of PTCL may be primary or secondary. Diagnosis of histiocytosis may be difficult, requiring clinical-pathological correlation. We describe a laryngeal atypical histiocytic lesion (AHL) and a nasal PTCL, NOS with cutaneous involvement in the same patient presenting with peculiar histopathologic and immunophenotypic features. The laryngeal neoplasm showed morphological and immunophenotypic evidence of histiocytic differentiation and does not fit any other category of the WHO classification nor the revised classification of histiocytosis. The nasal and cutaneous lesions presented features close to natural killer/T-cell lymphoma and gamma-delta T-cell lymphoma but did not meet accurately the WHO criteria. A somatic activating Q61K mutation was found on exon 3 of the NRAS gene in both AHL and PTCL, NOS. The mutation on NRAS gene in both AHL and PTCL, NOS may suggest a common origin from a precursor cell.

Dermatofibrosarcoma protuberans (DFSP) is an uncommon soft-tissue tumor characterized by a relatively high risk for local recurrence and low risk for metastasis. Many histopathologic variants of DFSP have been described, including the fibrosarcomatous and myoid variants, which may obscure the diagnosis in some cases, especially when arising in unusual locations. Of all the variants described so far, the only one with prognostic relevance is the FS-DFSP variant, which implies tumor progression and a higher possibility for metastasis. The authors report a case of a giant DFSP, located on the vulvar area, which histopathologically showed areas of fibrosarcomatous and myoid differentiation, and discuss the importance of the myoid variant in regards of the debated histogenesis of DFSP.

Follicular malignant melanoma (FMM) is a rare variant of melanoma arising on sun-damaged skin of elderly patients. It is characterized histopathologically by a prominent involvement of 1 or 2 adjacent hair follicles. The authors report 3 new cases of FMM (M:F = 2:1; age range, 23-67 years; median age, 50 years) located on the scalp, cheek, and upper back. Complete effacement of the hair follicle, replaced by neoplastic melanocytes, was observed in 1 case. The interfollicular epidermis and adventitial dermis were involved in all 3 cases. Our series shows that FMM is not restricted to elderly patients but may arise also in young individuals without association with chronic sun damage. FMM should be distinguished from folliculotropic metastases of melanoma and from atypical melanocytic nevi. Although the histopathological features and the term FMM may suggest a derivation from melanocytes of the hair follicle, the exact origin of neoplastic cells is yet unclear, and at least some of these cases may represent folliculotropic examples of primary epidermal malignant melanoma.

Late-onset focal dermal elastosis is a rare disorder of elastic tissue, characterized by a local accumulation of elastic fibers in the mid and deep reticular dermis. This disorder occurs mainly in elderly people and consists of multiple yellow papules that are typically distributed on the sides of the neck and flexural areas, closely resembling pseudoxanthoma elasticum from the clinical point of view. We report 2 sisters who have presented with a 20-year history of multiple yellow papules, mainly located on the dorsum of their hands. They also had few lesions of similar morphology scattered on the anterior aspects of their wrists, thighs, and lower abdomen. Histopathologic study demonstrated a focal increase in thick, interlacing elastic fibers in the mid and deep reticular dermis. The most striking features of our cases were the early age of clinical presentation, the familial involvement, and the predominantly acral distribution of the lesions.

We report the unique association of primary cutaneous marginal zone B-cell lymphoma and Rosai-Dorfman disease (RDD)-type histiocytic infiltrates involving the same lesions. The patient was an 82-year-old woman with 3 long-standing, well-circumscribed firm erythematous to brownish plaques on her left arm, right scapular area, and lumbosacral area. Histopathologic examination disclosed a dermal and subcutaneous nodular lymphoplasmacytic infiltrate with evidence of germinal center colonization and light-chain restriction and sheets of S-100 CD68-positive histiocytes with ample pale cytoplasm and occasional emperipolesis of lymphocytes. The neoplastic plasma cells expressed immunoglobulin (Ig) G4. A review of 14 examples of cutaneous RDD showed a substantial number of IgG4-positive cells in only 3 of them, and a review of 8 primary cutaneous marginal zone B-cell lymphomas disclosed only 2 with significant IgG4 expression. The coexistence of lymphomas and RDD has been rarely reported in the literature but only seldom involving the same lymph node and-to the best of our knowledge-never in the skin.

Giant congenital melanocytic nevi (GCMNs) represent a distress to patients for 2 reasons: one is disfigurement, and the other is the increased risk of developing secondary melanocytic tumors, such as benign proliferative nodules (BPNs) and malig- nant melanoma (MM). BPN present as a rapid growth nodule arising within a congenital melanocytic nevus (CMN) that often ulcerates, occurs in children younger than 2 years of age. BPNs arising within a CMN are exceedingly rare after childhood, and very few cases have been described in adults. Despite the worrisome clinical and histologic findings of BPN, most laboratory investigations seem to support their benignity. The distinction between MM and BPN is extremely important, but the histopathology of BPN of GCMN can be a challenge to differentiate from MM. In the recent years, molecular tests that investigate DNA copy number alterations such as fluores- cence in situ hybridization and comparative genomic hybridization have shown promise to help guide the diagnosis of ambiguous melanocytic proliferations arising within CMNs. We report the case of a 22-year-old woman with a nodule arising in a GCMN and with an axillary mass suggesting a nodal metastasis of melanoma, and discuss the unusual clinical, histopathologic, and molecular findings that make this case particularly interesting.

Postirradiation pseudosclerodermatous panniculitis is a rare panniculitic disorder induced by radiotherapy. Clinically, it consists of an indurate plaque localized on the irradiated area that may appear months or even years after radiotherapy was administered. Histopathologically, postirradiation pseudosclerodermatous panniculitis is characterized by a mostly lobular panniculitis without vasculitis, with lipophagic granuloma involving the fat lobules, a variable inflammatory infiltrate of lymphocytes and plasma cells and sclerotic thickening of the connective tissue septa of the subcutis. We report 3 additional cases of this rare variant of panniculitis, in which besides the panniculitis findings, dermal vessels showed sclerotic vessel walls and atypical bizarre fibroblasts with large pleomorphic and hyperchromatic nuclei were interstitially arranged between collagen bundles of the dermis. These dermal findings represent additional histopathologic features supporting the pathogenic role of the radiotherapy in the development of this rare variant of panniculitis.