Journal of Cutaneous Pathology最新文献

Leukemia cutis is defined as involvement of the epidermis, dermis, and subcutaneous tissue with a systemic leukemia. It is associated with a poor prognosis and can be a sign of advanced leukemia. This case series describes a distinct pattern of leukemic cell involvement in the skin that differs from classic leukemia cutis. These cases are characterized by a sparse leukemic cell infiltrate typically associated with an underlying inflammatory tissue reaction pattern. This is suggestive of “spillover” rather than primary infiltration. This phenomenon may not uniformly carry the same poor prognosis as classic leukemia cutis and emphasizes the need for further research to guide diagnosis and management.

A 70-year-old immunocompetent woman presented to dermatology with a firm, asymptomatic subcutaneous nodule on her right forearm that had persisted for 1 year. The nodule measured approximately 13 mm on examination, was mobile, and showed no epidermal changes. Histopathology revealed numerous well-formed dermal granulomas with lymphocytic infiltrates and abundant acid-fast bacilli on Fite stain. PCR and sequencing of the hsp65 and rpoB genes from two separate tissue samples identified a previously undescribed bacterial species of the Mycobacteriales order, showing only distant similarity to M. leprae , M. ulcerans , and M. marinum . Although nontuberculous mycobacteria (NTM) are common environmental organisms that typically cause cutaneous infections following trauma, surgery, or cosmetic procedures, no recent inciting event was reported during the infectious disease consultation. The patient did note a similar nodule had been excised from a different location decades earlier and described as “tuberculous,” though detailed records were unavailable. This history suggests the possibility of an earlier environmental exposure resulting in a latent, subclinical, long-term infection. No further treatment was pursued due to the absence of systemic symptoms and additional cutaneous lesions after excision.

Primary effusion lymphoma (PEL) is a rare B-cell lymphoma that is most often seen in immunocompromised patients with human herpesvirus-8 (HHV-8) and Epstein–Barr virus (EBV) infections. PEL typically affects body cavities with occasional involvement of other organs (extracavitary PEL). We present an unusual case of primary cutaneous extracavitary PEL without body cavity effusions. A 56-year-old man with uncontrolled HIV (CD4 count 50, viral load 264 copies/mL) presented with a 2-month history of fever, cough, and progressive dyspnea. Physical examination revealed bilateral inner thigh erythema and induration. Laboratory evaluation showed an elevated EBV viral load. Imaging studies did not reveal body cavity effusions. Skin biopsy from the thigh demonstrated a deep dermal and subcutaneous infiltrate of large pleomorphic lymphoid cells. The atypical cells were CD45+, CD138+, CD3+, HHV8+, EBV in situ hybridization (ISH)+, CD20-, CD79a- and PAX5 negative. Our case highlights a rare primary cutaneous manifestation of extracavitary PEL. It is important for dermatopathologists to be aware of the histopathological features of extracavitary PEL and its unusual immunophenotype (CD138+, negative for B-cell markers with aberrant expression of T-cell markers), which could represent a potential diagnostic pitfall. HHV-8 and EBER ISH positivity is crucial for the diagnosis of cutaneous extracavitary PEL.

We present a case of an 84-year-old female with an isolated and asymptomatic 1.0 cm red papule on the left medial knee. A shave biopsy revealed a diffuse atypical lymphoid infiltrate in the dermis with epidermotropism, diffuse expression of CD30 and positive T-cell receptor (TCR) gamma-delta immunophenotype. Fluorescence in situ hybridization (FISH) identified a chromosomal rearrangement involving dual-specificity phosphatase-22 (DUSP22) and interferon regulatory factor-4 (IRF4). Next generation sequencing (NGS) indicated a low tumor mutational burden with no gene variants. Upon follow-up, there was no evidence of residuum or recurrence. The findings provided the best support for an unusual presentation of lymphomatoid papulosis (LyP) with DUSP22-IRF4 gene rearrangement and TCR gamma-delta phenotype. LyP was favored over anaplastic large-cell lymphoma due to spontaneous resolution and lack of systemic involvement. The clinical history and immunohistochemistry excluded mycosis fungoides or other lymphomas. LyP associated with DUSP22-IRF4 gene rearrangement is rarely documented in the literature. This is a unique presentation of LyP with concurrent DUSP22-IRF4 gene rearrangement and TCR gamma-delta phenotype along with an indolent clinical course. Diagnosing LyP can be particularly challenging due to its histologic similarities with other cutaneous lymphomas, underscoring the importance of distinguishing this relatively benign condition from more aggressive malignancies.