title: Lymphohistiocytic anaplastic large cell lymphoma involving skin: a diagnostic challenge.
abstract: Systemic anaplastic large cell lymphoma (ALCL) involving the skin should be differentiated from primary cutaneous CD30-positive T-cell lymphoproliferative disorders. The lymphohistiocytic variant of ALCL (LH-ALCL) is rich in reactive histiocytes with relatively few neoplastic cells, which pose a diagnostic challenge. We present a case of LH-ALCL involving skin mimicking granulomatous inflammation. A 30-year-old woman presented with cervical lymphadenopathy and multiple non-tender, non-itching, erythematous papules over the neck, chest, and abdomen. Biopsy of the cervical lymph node showed LH-ALCL with null cell phenotype. Microscopically, the cutaneous lesion was located predominately around the hair follicle, with numerous reactive histiocytes and scanty medium-sized lymphoma cells expressing CD30 and anaplastic lymphoma kinase (ALK) protein. Furthermore, an ALK gene rearrangement was demonstrated by locus-specific interphase fluorescent in situ hybridization, confirming cutaneous involvement with LH-ALCL. LH-ALCL involving the skin is a rare event, and the numerous reactive histiocytes may mask scanty tumor cells. In addition to B-and T-cell markers, (dermato) pathologists must be aware of this entity in cutaneous lymphohistiocytic proliferations and perform immunostaining for CD30 and ALK to reach a correct diagnosis.
authors.affiliation: Department of Pathology, Chi-Mei Medical Center, Tainan, Taiwan. cmh5301@mail.chimei.org.tw
authors.forename: Shih-Sung
authors.initials: SS
authors.lastname: Chuang
authors.forename: Yen-Chuan
authors.initials: YC
authors.lastname: Hsieh
authors.forename: Hongtao
authors.initials: H
authors.lastname: Ye
authors.forename: Wei-Shou
authors.initials: WS
authors.lastname: Hwang
mesh_terms: D000328:Adult; D000077548:Anaplastic Lymphoma Kinase; D015321:Gene Rearrangement; D006644:Histiocytes / Q000473:pathology; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D017730:Ki-1 Antigen / Q000378:metabolism; D017728:Lymphoma, Large-Cell, Anaplastic / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008297:Male; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*
chemical_list: D017730:Ki-1 Antigen; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases