A 82 y.o. woman comes in with what her family thought was a "bun" on the top of her head.

The lesion had been there 17 years.

what could it be?

Our patient had a cutaneous  leiomyosarcoma of the scalp.  This is a malignant smooth muscle tumor accounting for only 4% of head and neck sarcomas. The differential of the tumor may be problematic and they can be initially diagnosed as keloids.  Leiomyosarcomas have spindle shaped cells on pathologic evaluation and the more aggressive forms have frequent mitotic figures.

Leiomyosarcomas are divided into cutaneous and subcutaneous types.  Subcutaneous leiomyosarcomas are generally an aggressive type of cancer and  may double in size in four weeks. This is the type most often seen in ED when it presents as recurrent or metastatic disease.  In contrast the cutaneous form is slow growing and often does not metastasize. The origin is the arrector muscles found in hair follicles.

If it is resected, this cutaneous type generally has an excellent outcome.

subcutanous leiomyosarcomas are often aggressive

Leiomyosarcomas which are subcutaneous are often found in women in the retroperitoneum. They are thought to arise from leiomyomas.  They can also be found in the GI viscera, extremities and blood vessels.  The retroperitoneal and vascular leiomyosarcomas have the worst prognosis.  Pleural leiomyosarcomas original in the serosal membranes of the lung  and can be diffuse resulting in mesothelioma or localized causing solitary fibrous tumors.  The solitary fibrous tumors are often benign and grow very slowly so they are often not discovered until they are very large.

benign solitary fibrous tumor of the pleura

Our patient had her tumor resected and the margins were free of tumor.  She elected to have no further treatment but will be monitored for recurrence.

Yaday J, Bakshi J, Chouhan M, Modi R.  Head and neck leiomyosarcomas. 2011 Indian J Otolaryngol Head Neck Surgery. 2013 Jul;65(Supple 1): 1-5.

Valeriani M , et al. Recurrent cutaneous leiomyosarcoma. J Exp clin Cancer res. 1998;17:83-85.

Sleiwah A, Clinton A, Herbert K. Delayed diagnosis of dermal leiomyosarcoma mimicking keloid scar..  BMJ 2018 Case Rep Jan 26:2018:bcr 2017222616. Doi: 10.1136/bcr-2017-222616.  PMID: 29374640

 Deneve J, Messina J, Bui M, et al.  Cutaneous leiomyosarcoma: a single institution experience of treatment and outcomes with a standardized margin of resection  2015 Cancer Control Oct : 20(4):307-312.