Case Report: A giant myopericytoma involving the occipital region of the scalp - a rare entity.

Herein we report a rare case of a giant myopericytoma presenting in a 16-year-old girl as a slowly progressive swelling involving the scalp in the occipital region. It was managed by complete excision. Histological examination of the lesion revealed  spindle-shaped cells forming characteristic rosettes around the blood vessels, and positive staining with smooth muscle actin.

Introduction

Myopericytoma is a rare entity. It mostly involves the skin and subcutaneous tissue of the distal extremities, torso, head and neck regions [1– 3]. Rarely does it involve the visceral sites [4, 5]. The spindle shaped cells of a myopericytoma show characteristic perivascular rosettes [6, 7]. Though mostly benign, rare cases of its malignant counterpart have been described [8]. We report a case of a giant myopericytoma involving the occipital region of the scalp of a young female, with good post-operative outcome following its complete excision. We believe this is the first case report of a giant myopericytoma involving this region.

Case report

A 16-year-old female from Butwal, Nepal presented to our outpatient clinic with a chief complaint of slow progressive swelling in the occipital region of the scalp, which she had been experiencing for the last 2 years. There was no history of trauma, pain, tinnitus, dizziness or discharge associated with the lesion, and no significant previous medical or surgical illnesses had been reported. Local examination revealed a soft to firm subcutaneous lesion measuring 9 × 8 cm 2, with no bruit within the lesion and normal overlying skin. There was no transmitted pulsation or cough impulse, and there were no palpable bony defects felt around the margins of the lesion. Lower cranial nerve examination was normal and cerebellar signs were negative. CT findings showed a homogeneously enhanced subcutaneous lesion ( Figure 1), but with no intracranial extension ( Figure 2).

Figure 1.

CT image showing homogeneously enhanced lesion in the scalp of occipital region.

Figure 2.

CT bone window showing a minimal osseous gap in the midline but no intracranial extension of the lesion.

After thorough counselling and consent, the patient was booked in for excision of the lesion. Adequate blood for transfusion was supplied because of the vascularity of the scalp and the giant size of the lesion. A midline incision was given, with the patient in the prone position. The edges of the lesion were vascular, with major pedicles from bilateral occipital arteries. Complete excision was undertaken ( Figure 3). Intra-operatively, the patient was transfused two pints of blood. Post-operative recovery was uneventful land she was discharged on the third day. Histological examination of the lesion revealed presence of spindle-shaped cells, forming characteristic rosettes around the blood vessels. Positive staining for smooth muscle actin (SMA) was highly suggestive for myopericytoma ( Figure 4), and the lack of mitotic cells or tissue necrosis confirmed its benign nature. Patient follow-up took place 2 weeks later, with no symptoms and a well healed wound. She was advised to come for periodic follow-ups every month.

Figure 3.

Excised specimen showing the giant lesion, of firm consistency and with no visible necrotic areas.

Figure 4.

Photomicrograph of tissue taken from the lesion excised from the patient, showing characteristic spindle cells forming perivascular rosettes and staining with smooth muscle actin (SMA).

Discussion

Myopericytoma has been described as being a type of perivascular tumor in the latest edition of World Health Organization classification of tumors of soft tissue and bone [6]. Histologically it is characterized by spindle cells forming perivascular rosettes and staining positive for SMA and negative for Desmin, Bcl2 and CD34 [9]. Though usually the size of a myopericytoma is less than 2 cm in superficial soft tissue, larger tumor size has been reported in the visceral locations [10, 11]. Some cases of the malignant form showing invasion, mitotic figures and necrosis have been described [6]. These malignant forms also show a high Ki-67 proliferative index, contrary to benign forms with low Ki-67 index [12].

Prior to diagnosing the myopericytoma, initially the major differential diagnosis was of a giant diffuse lipoma. Other differential diagnoses included other mesenchymal lesions, like desmin positive angioleiomyomas, glomus tumors in which epitheloid cells form rosettes, and solitary fibrous tumors, which do not form visible perivascular rosettes [13]. These can be differentiated on the basis of their characteristic immunohistological reactivity patterns, such as positive staining with SMA and often also with h-Caldesmon [9].

Recurrence of the tumor can occur, even in benign cases, so complete excision should be the goal [13]. Following complete excision, patients should return for periodic follow-ups despite the benign nature of the tumor.

Conclusion

Though a rarity, myopericytoma should be ruled out prior to surgical management of subcutaneous lesions, because sometimes the high vascular nature of the lesion may impose difficulties during its excision and pose a risk to the patients’ life if adequate arrangements for blood transfusions have not been made.

Consent

Written informed consent for publication of the patient’s details and their images was obtained from the guardian of the patient.

İt is a well written article and contains novel knowledge.

It is an original article but provides minimal sufficient details for practitioners.

It includes a background of the case's history and progression and provides details of any physical examination and diagnostic tests, treatment given and outcomes.

It includes a discussion of the importance of the findings that also describes their relevance to future understanding of disease processes, diagnosis or treatment.

I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

This case is very interesting, and describes the rare entity which will serve in the medical practice.

The title is appropriate for the content of the article and the abstract represent a suitable summary of the work.

The design, methods and analysis of the results from the study been explained and are they appropriate for the topic being studied.

Also, the conclusions are sensible, balanced and justified on the basis of the results of the study.

I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

I congratulate Dr Munakomi et al for an interesting article.

The following are my comments:

The article is well written and highlights a rare pathological entity which may thought of in the differential diagnosis of large scalp lesions.

A clinical photograph outlining the lesion would be interesting.

There are no MRI images. Any large scalp tumor should have a pre-op MRI. If MRI images are available kindly upload those.

English language editing is recommended e.g. instead of using the word ‘pint’ the word ‘unit of blood’ seems more appropriate.

There is no discussion on the radiological characteristics of the tumor and its differential diagnosis.

It would be interesting to have a tabulated review of literature of myopericytomas of the scalp.

I would also recommend the authors provide a table of differential diagnosis of various pathologies and their immunohistochemical characterizations.

Although the take home message appears to be a high clinical suspicion in order to prevent excess blood loss intra-operatively, the authors do not specifically mention any particular measures, if any, they took to minimize bleeding intra-operatively.

A two week follow up is too short for any tumor and some discussion on how frequent (%) is the recurrence after complete excision and what is the treatment strategy for recurrences.

Final Verdict: Paper may be accepted for indexing with the relevant changes.

I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.