Skin diseases: New developments and findings in pathology

The latest findings in dermatological pathology - from newly discovered diseases to the background of "COVID toes" are briefly and concisely summarised.

New diseases, prognosis markers and findings on “COVID toes”

The latest findings in dermatological pathology - from newly discovered diseases to the background of "COVID toes" are briefly and concisely summarised.

Vascular diseases

Earlier this year, Semkova et al. described a new disease: "poikilodermatous plaque-like hemangioma". Phenotypically, this skin disease manifests itself as reddish-livid, haemangious plaques, which are mainly located on the lower extremities. Histologically, band-shaped vascular proliferations within the superficial skin layers can be detected - with fibrous, oedematous changes, and a loss of elastic fibers.

Another rather rare vascular disease is angiosarcoma of the lymphatic type, a special form of angiosarcoma. Local swelling with lymphatic infiltrations occurs, especially in older patients and mainly in the area of the head and neck. This form of angiosarcoma expresses two markers, podoplanin and Prox-I, which can be used to detect the disease. Overall, this subtype has a better prognosis than other cutaneous angiosarcomas.

Lymphomas

Anaplastic large T-cell lymphoma is usually anaplastic lymphoma kinase (ALK)-negative, and ALK detection typically indicates systemic involvement. An exception is ALK-positive large cell anaplastic T-cell lymphoma, which is a special subtype with single, localized lesions without systemic involvement. The prognosis is no different from ALK-negative forms and in this case too, radiotherapy should be used as standard treatment.

Lymphoproliferative diseases

The Primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder (PCSMLPD) is a benign lymphoproliferative disease with the development of nodular tumors, especially in the head and neck area. In the course of the disease, spontaneous regressions can often occur (in 32% of cases). Genetic engineering revealed a mutation in the TCR gene in 68% of the cases examined, and a mutation in the DNMT3A gene was found in one of 13 affected persons.

Melanocytic lesions of the skin

A new prognosis marker for malignant melanoma was investigated. In addition to the standard tumor thickness according to Breslow (Breslow, 1970), the determination of the invasion width in a retrospective study has proven to be a good prognosis marker with regard to the probability of survival and metastasis-free intervals.  In the future, this new marker could be determined in addition to BT.

A new immunohistochemical marker has also been developed in the field of melanoma diagnostics. PRAME (Preferentially expressed antigen in melanoma) is a melanoma-associated antigen that was detected in the study in over 90% of malignant melanomas. Compared to previous markers, PRAME is faster and cheaper. PRAME can also be used for differentiation in unclear melanocytic changes.

COVID-19-associated skin lesions

In the context of the COVID-19 disease, cutaneous lesions have been observed in the distal lower extremities (mainly toes) of some patients. These so-called "COVID toes" have histological similarities to idiopathic chilblains or those resulting from systemic lupus erythematosus. In the biopsies of these lesions, SARS-CoV-2 was detected in the epithelial cells.

Reference:
Dr. J. M. Mascaro, Barcelona, Spain "New developments in dermatopathology", EADVirtual 2020, 30.10.2020

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