T-cell-rich angiomatoid polypoid pseudolymphoma of the skin L98.8

T-cell-rich angiomatous polypoid pseudolymphoma of the skin (TRAPP) is a rare, benign lymphoproliferative disease that was first described by Kempf et al. in 2011. It belongs to the so-called pseudolymphomas of the skin, i.e. reactive (non-malignant) lymphoid proliferations of the skin that can clinically and histologically resemble a lymphoma.

A broad age group from 16 to 71 years with a female predominance is affected (Sandhya V et al. 2024).

There is a preference for the head (often on the earlobe or face) and trunk. The knee, shoulder and thigh are less frequently affected.

The lesions are solitary and present as small (<1 cm), consistent, painless, red to livid, polypous or nodular, broad-based papules.

Mostly solitary, polypoid or nodular skin lesion with dense dermal infiltrate of lymphocytes with a variable number of mixed plasma cells and histiocytes. Immunohistochemical examination reveals a predominance of CD3 over CD20, and CD4 T cells over CD8 cells; few B cells. Prominent capillary proliferation is conspicuous. No atypical cytomorphology or destructive growth. No evidence of monoclonal TCR gene rearrangement.

Cutaneous T-cell lymphoma (e.g. mycosis fungoides): Years of progression with precursors, histology is diagnostic

Angiomatous tumors (e.g. Kaposi's sarcoma): mostly multiple tumors, histology is diagnostic

Lymphadenosis cutis benigna: broad-based soft nodules, histology is diagnostic

Lymphomatoid papulosis: rapidly growing, frequently ulcerated, histology is diagnostic

Acral pseudolymphomatous angiokeratoma in children (APACHE): usually multiple papules; histology is diagnostic (Ramsay B et al. 1990).

Angiolymphomatoid hyperplasia with eosinophilia (Wells and Whimster): Head and neck area, miet multiple, recurrent after surgery; histology: predominantly vascular proliferate.

Angioplasmacellular hyperplasia: rare lesion with vascular proliferation and reactive plasma cell infiltration. Patients present with one or a few nodules or papules. Common localizations are the face, scalp, trunk and legs. The dermal infiltration consists mainly of plasma cells, which make up between 70 and 90 % of the infiltration. Lymphocytes and eosinophils are present in small numbers. Histiocytes are absent

Angiolymphoid hyperplasia with high endothelial venules (ALH-HEV) (APACHE variant/ Fernández-Figueras MT et al. 2001)

Acral pseudolymphomatoid angiokeratoma (papular pseudolymphoma)

Papular angiolymphoid hyperplasia with high-endothelial features in adults and children (PALEFACE)

Amelanotic melanoma: dermoscopy with pigment residues, histology is diagnostic

Excision is usually curative.

Benign, no risk of recurrence after excision. No progression to true lymphoma described.

This article reports on the case of a 13-year-old female patient who had had a completely asymptomatic skin-colored papule on the inside of her right elbow for six months. The papule had a diameter of 0.4 cm. There was no evidence of insect bites or medication. The clinical differential diagnosis included lupus vulgaris, tuberculosis verrucosa cutis and sarcoidosis. A punch biopsy was taken and sent for histopathologic examination.

Microscopic examination revealed a thinned epidermis with basket-weave keratinization. The superficial and middle dermis showed a dense diffuse infiltration of lymphocytes, plasma cells and histiocytic clusters. The deep dermis shows a perivascular infiltration of plasma cells and lymphocytes. The dermal infiltration extends very close to the overlying atrophic epidermis. The border zone was focally present. However, no epidermotropism was observed. Prominent vessels lined by bulging endothelial cells were present amidst the dermal infiltrate. Special staining with Giemsa and Fite was negative for microbial organisms. Immunohistiochemistry showed a predominance of CD3- over CD20-positive lymphocytes. Otherwise, a mixture of CD4- and CD8-positive T cells and accumulations of CD68-positive histiocytes were found.

1. Fernández-Figueras MT et al. (2001) Cutaneous angiolymphoid hyperplasia with high endothelial venules is characterized by endothelial expression of cutaneous lymphocyte antigen. Hum Pathol 32:227-229.
2. Peñaflor-Téllez Y et al. (2019) Immune Response Modulation by Caliciviruses. Front Immunol 10:2334.
3. Ramsay B et al. (1990) Acral pseudolymphomatous angiokeratoma of children. Arch Dermatol 126:1524-5.
4. Sandhya V et al. (2024) T-cell rich angiomatoid polypoid pseudolymphoma: a novel cutaneous pseudolymphoma. Indian J Dermatol 59:361-363.
5. Sano Y et al. (2019) T cell-rich angiomatoid polypoid pseudolymphoma arising after local injury on the lip of a pregnant woman. J Eur Acad Dermatol Venereol 33:e164-e166.