Expression of Peripheral Node Addressins by Plasmacytic Plaque of Children, APACHE, TRAPP, and Primary Cutaneous Angioplasmacellular Hyperplasia

High-endothelial venules are a common feature of 3 types of cutaneous pseudolymphomas: pretibial lymphoplasmacytic plaque (PLP) of children, acral pseudolymphomatous angiokeratoma of children (APACHE), and T-cell rich angiomatoid polypoid pseudolymphoma (TRAPP). In addition, primary cutaneous angioplasmacellular hyperplasia (PCAH) overlaps with these other 3 conditions. We intend to study the expression of peripheral node addressins in PLP, APACHE, TRAPP, and PCAH. We studied 1 case of PLP, 2 cases of APACHE, 2 cases of TRAPP, and 2 cases of PCAH. Immunostainings for MECA-79 and WT-1 were obtained in all cases. All cases showed a dense lymphohistiocytic dermal inflammatory infiltrate with abundant plasma cells. In addition, HEV were prominent in all cases. Cases of PLP, APACHE, and TRAPP expressed MECA-1. Cases of PCAH did not express MECA-1. Although PLP, APACHE, and TRAPP seem to fall under the same morphologic spectrum with different clinical representations, PCAH seems to be a different entity, with histopathologic peculiarities and a different immunophenotype.

Cutaneous Angiolymphoid Hyperplasia in a Dog

A 5-year-old male miniature dachshund was presented with a dermal nodule on the left forelimb that increased to 5 mm in diameter over a 2-month period. Grossly, the nodule was firm, and both the external and cut surfaces were homogeneously pale pink in colour. Microscopically, the nodule was comprised of mainly plump endothelial cells and inflammatory cells; among the latter, lymphocytes were predominant, with few scattered plasma cells, mast cells and macrophages. Lymphoid follicles with germinal centres were often observed. Mitotic figures were not observed amongst the endothelial cells. Immunohistochemically, the endothelial cells were positive for vimentin, factor VIII-related antigen and CD31, and the surrounding cells were positive for smooth muscle actin. Lymphocytes expressed CD3 or BLA36. These findings led to a diagnosis of cutaneous angiolymphoid hyperplasia. To the best of our knowledge, this is the first report of a cutaneous proliferative disorder comprising an admixture of proliferating vascular endothelial cells and lymphocytic infiltration with follicle formation in a dog.

Acral angiokeratoma-like pseudolymphoma in a middle-aged woman

Acral angiokeratoma-like pseudolymphoma is a rare type of pseudolymphoma presenting as dark-red papules on the hand or foot. We describe a 59-year-old woman who presented with an unusual unilateral, clustered aggregate of scaly violaceous papules on the toe with an indolent course. Skin biopsy showed a prominent vascular proliferation associated with a dermal infiltrate of monoclonally rearranged T-follicular helper phenotype T-cells, in keeping with CD4+ small/medium T-cell lymphoproliferative disorder (SMPTC-LPD). Based on the unique clinical morphology, distribution of the lesions and dermoscopic appearance, a clinicopathologic diagnosis of acral angiokeratoma-like pseudolymphoma was favored. This case demonstrates the importance of clinicopathological correlation in such diagnostically challenging patients who present with overlapping features on the spectrum of pseudolymphoma and cutaneous T-cell lymphoma.

Acral pseudolymphomatous angiokeratoma of children: a case report with immunohistochemical study of antipodoplanin antigen

Acral pseudolymphomatous angiokeratoma of children (APACHE) is characterized by multiple angiomatous papules on the hands and feet in children. Here, we report a case of APACHE in a female patient followed up from 13 to 19 years of age with a dark red lesion on the center of the dorsum of the right thigh. Histologically, vacuolar alteration and exocytosis of lymphocytes, and specific dense cellular infiltration beneath the epidermis to the reticular dermis were found. On immunolabeling study, the lesion vessels were found to be positive for both the lymphatic endothelium-specific marker podoplanin and blood vessel-specific marker CD34. These findings suggested that APACHE is a type of vascular malformation.