Keratoacanthoma or cutaneous squamous cell carcinoma revealing a DNA mismatch repair default (Muir-Torre Syndrome)

Keratoacanthoma (KA) and well-differentiated cutaneous squamous cell carcinoma (cSCC) are hardly distinguishable clinically and histologically. They both can be seen in patients with hereditary non-polyposis colorectal cancer (HNPCC) or Lynch Syndrome, corresponding to DNA microsatellite instability. In our case, a young man had the excision of two rapidly growing skin tumours for which distinction between KA and cSCC was initially clinically and pathologically challenging. The diagnosis of well-differentiated cSCCs was made and the patient was treated with surgery. Ten years after the first cSCC, he was diagnosed with Muir-Torre syndrome, a variant of Lynch syndrome, with an heterozygote mutation of the MSH2 gene. This later diagnosis allowed to screen his family members for the same mutation and to adopt an appropriate follow-up regarding the risk of digestive tumours for him and his family. Furthermore, it is important to know that, in case of non-resectable cSCC occurring in this patient, immunotherapy using anti-PD1 antibody would probably be effective due to the known increased immunogenicity of MMR deficient tumours.

Pityriasis lichenoides: a clinical and pathological case series of 49 patients with an emphasis on follow-up

The classification of pityriasis lichenoides (PL) into pityriasis lichenoides et varioliformis acuta (PLEVA), PL chronica (PLC) or febrile ulceronecrotic Mucha-Habermann disease (FUMHD) mixes clinical and chronological features. In this retrospective monocentric study, we aimed to investigate the relevance of the classification in routine practice. We included 49 patients (25 women, median age 41 years). The lesions were papular in 76% of patients, necrotic in 12%, and mixed in 12%. We found three histological patterns: "classical" (65%), "lymphomatoid" (13%), and "mild" (22%). The "lymphomatoid" pattern was associated with necrotic presentation and the "mild' pattern with papular lesions (p=0.012). Among the 27 patients with follow-up, 18% had relapses and 44% a chronic form. One patient had mycosis fungoides. Neither clinical nor histological aspects were correlated with disease progression. Clinical and histological pictures reflect more the intensity of epidermal injury rather than disease course. "Pityriasis lichenoides" should be preferred to the classical PLEVA/PLC classification.

[Acute pericarditis and tamponade: An unusual revelation of a visceral tuberculosis]

Tuberculosis is a common pulmonary disease, which is still endemic in disadvantaged communities. Pericarditis is a rare but very lethal visceral localization. The authors report the case of a 58-year-old man, without neither medical history nor social risk, who presented a cardiac tamponade as the first and atypic manifestation of a visceral tuberculosis.