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. 2023 Aug;83(2):310-319.
doi: 10.1111/his.14940. Epub 2023 May 18.

Recurrent PAK2 rearrangements in poroma with folliculo-sebaceous differentiation

Thibault Kervarrec  1   2   3 , Daniel Pissaloux  4   5 , Sandrine Paindavoine  4 , Franck Tirode  5 , Amélie Osio  6 , Samia Mourah  7 , Fanélie Jouenne  7 , Pierre Sohier  3   8   9 , Eduardo Calonje  10 , Agnes Pekar  10 , Evelyn Vanesa Erazo Luna  10 , Keisuke Goto  11   12   13   14 , Flore Delalande  15 , Eric Frouin  3   16 , Nicolas Macagno  3   17 , Françoise Drouot  3   18 , Monique Faisan  3   19 , Bernard Cribier  3   20 , Maxime Battistella  3   6   21 , Arnaud de la Fouchardière  3   4
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Recurrent PAK2 rearrangements in poroma with folliculo-sebaceous differentiation

Thibault Kervarrec et al. Histopathology. 2023 Aug.

Abstract

Aims: Poroma is a benign adnexal neoplasm with differentiation towards the upper portion of the sweat gland apparatus. In 2019, Sekine et al. demonstrated recurrent YAP1::MAML2 and YAP1::NUTM1 fusion in poroma and porocarcinoma. Follicular, sebaceous and/or apocrine differentiation has been reported in rare cases of poroma and whether these tumours constitute a variant of poroma or represent a distinctive tumour is a matter to debate. Herein we describe the clinical, immunophenotypic, and molecular features of 13 cases of poroma with folliculo-sebaceous differentiation.

Methods and results: Most of the tumours were located on the head and neck region (n = 7), and on the thigh (n = 3). All presented were adults with a slight male predilection. The median tumour size was 10 mm (range: 4-25). Microscopically, lesions displayed features of poroma with nodules of monotonous basophilic cells associated with a second population of larger eosinophilic cells. In all cases, ducts and scattered sebocytes were identified. Infundibular cysts were present in 10 cases. In two cases high mitotic activity was noted, and in three cases cytologic atypia and areas of necrosis were identified. Whole transcriptome RNA sequencing demonstrated in-frame fusion transcripts involving RNF13::PAK2 (n = 4), EPHB3::PAK2 (n = 2), DLG1::PAK2 (n = 2), LRIG1::PAK2 (n = 1), ATP1B3::PAK2 (n = 1), TM9SF4::PAK2 (n = 1), and CTNNA1::PAK2 (n = 1). Moreover, fluorescence in situ hybridisation (FISH) analysis revealed PAK2 rearrangement in an additional case. No YAP1::MAML2 or YAP1::NUTM1 fusion was detected.

Conclusion: Recurrent fusions involving the PAK2 gene in all analysed poroma with folliculo-sebaceous differentiation in this study confirms that this neoplasm represents a separate tumour entity distinct from YAP1::MAML2 or YAP1::NUTM1 rearranged poromas.

Keywords: PAK2; apocrine poroma; folliculo-sebaceous differentiation; holocrine poroma; infundibular adenoma.

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References

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