Leiomyomas are benign tumors of smooth muscle. The distribution of such tumor’s mirrors the dis-tribution of smooth muscle tissue in the body. Therefore, these are more common in the genitouri-nary and gastrointestinal tracts. They are less frequent in the skin and rare in the deep soft tissues. Several types of leiomyomas have been described for classification purposes.
These include- cutaneous leiomyoma (leiomyoma cutis), angiomyomas (vascular leiomyoma), leiomyomas of deep soft tissue origin, leiomyomatosis peritonealis disseminata (represents a diffuse metaplastic response of the peritoneal surfaces), and finally benign genital stromal tumor’s.
The type which is relevant to this discussion is the leiomyomas of deep soft tissue origin which is the rarest form of leiomyoma ^[1]. Histologically, these tumor’s show fascicles of well-differentiated, uniform, elongated spindle-shaped cells with abundant eosinophilic cytoplasm which resemble smooth muscle cells. They show no necrosis, at most only mild atypia and <1 mitoses/50 high-power fields (HPF) [1, 2, 3]. As such, leiomyomas in the spine are extremely rare with only a limited number of studies describing them in English literature. Out of these nine were cases of Benign metastasizing leiomyoma (BML) [4, 5, 6, 7, 8, 9, 10, 11], and only 2 were Primary leiomyomas of the Spine [3, 12]. The tumor’s show strong reactivity to smooth muscle markers such as caldesmon, smooth muscle actin (SMA), and desmin with very low Ki-67 proliferative index (<2%) [2, 3, 5, 8].

A 15-year-old student had swelling over the nape of the neck for 4 years with slight difficulty in neck movements for 6 months (Fig. 1). Four years ago he noticed a swelling at the nape of the neck on the right side initially the size of a pea. It was not associated with pain. Over 4 years the swelling gradually increased in size with rapid increase in the last 6 months causing difficulty in moving the neck. The patient did not experience any radiation in the upper or lower limbs and had normal bladder and bowel function. On examination, a 10 × 8 cm firm, non-tender, non-pulsatile swelling is present at the nape of the neck more on the right side extending from the occiput nuchal line and crossing up to the posterior border of sternocleidomastoid. The skin over the swelling was non-adherent and the rotation was terminally restricted towards the right. Routine X-ray’s and magnetic resonance imaging were suggestive of a soft tissue mass in the inter-muscular plane on the posterior aspect more on the right side with a cystic component and causing thinning of the C2 lamina with no intraspinal extension (Fig. 2, 3). On serological examination, the erythrocyte sedimentation rate, C-reactive protein and total counts were found to be normal. The patient was immunocompe-tent as per the ELISA report. Percutaneous biopsy was and diagnosis of a benign spindle cell benign tumor was made. Posterior en-bloc excision was planned and the lesion blog with the entire capsule was excised (Fig. 4) and sent for histopathology which revealed that the lesion showed spindle cells arranged in interlocking bundles leiomyoma (Fig. 5) with immunohistochemistry (IHC) studies showing strong positivity for desmin (Fig. 6). The patient has significant relief from symptoms post-operatively with some residual numbness over the nape of the neck which improved at 6 weeks follow-up. Recent follow-up (3 years post-operatively) showed no clinical or radiological evidence of recurrence.

Primary leiomyomas of deep soft tissue origin is exceedingly rare as compared to their malignant counterpart. These are of two distinct types somatic and gynecologic, which differ in their presentation ^[1]. The less common somatic leiomyoma affects both sexes equally ^[1]. They measure several centimeters at presentation and about one-third also contain calcification. In contrast, the leiomyoma of gynecologic type occurs exclusively in women, usually in the peri-menopausal period. They closely resemble the standard uterine leiomyomas on gross and histo-pathological evaluation. This type typically displays both nuclear estrogen and progesterone receptor proteins ^[1].
Primary leiomyomas of the head and neck region are rare due to the paucity of smooth muscle in this region [2, 14, 15]. Leiomyomas have been described at locations like the oral cavity, nasal cavi-ty, nasopharynx, larynx, esophagus, and orbits [14, 15, 16]. Majority of the primary leiomyomas of the neck arise from the esophagus ^[2]. Leiomyomas of intra-spinal origin are extremely rare with two previous case reports describing leiomyomas arising from the thoracic spine [3, 12]; whereas, there is only one report of leiomyoma arising from the cervical spine. We believe that ours is an extremely rare case of a primary neck leiomyoma not arising from the esophagus with only two such cases described in literature [2, 14].
The pathogenesis of such tumors is uncertain. According to a theory put forward by Steel et al. such tumors arise from the smooth muscle component of blood vessels ^[12]. More modern studies postu-late the possible role of aberrant undifferentiated mesenchyme within the blood vessels [2, 14, 15]. In addition, association of concomitant viral infections such as Epstein-Barr virus [3, 17, 18, 19] and human immunodeficiency virus with smooth muscle tumors is well known [12, 20, 21, 22, 23]. Our case was again unique in this respect with the patient being immuno-competent.
The clinical presentation is characterized by the location of the tumor which secondary to its mass effect may present as a progressive swelling with secondary restriction in neck movements, difficul-ty feeding or breathing with associated malnourishment ^[2]. Intraspinal tumors may result in radicu-lopathy, spasticity as well as motor and sensory neurodeficit [3, 12]. In our case, the features gradu-ally worsened over a period of 4 years which is in accordance with other studies [3, 6, 9, 11, 12].
On histopathological evaluation the tumor comprises multiple interlacing fascicles or bundles of well-differentiated spindle-shaped acidophilic/eosinophilic cells which have blunt-ended, elongated nuclei also called as cigar-shaped nuclei. [2, 3, 12]. Somatic leiomyomas show no necrosis, only mild atypia if at all and virtually no mitotic activity with <1 mitosis/50 HPF ^[1]. Typically, IHC is assertive in ruling out other differential diagnoses with the tumor cells showing strong reactivity to smooth muscle markers such as SMA, desmin, and caldesmon. The Ki-67 proliferative index is also <2%. [2, 3, 5, 8]. Soft tissue leiomyomas of gynecologic type, either primary or BML may exhibit positivity for estrogen and progesterone receptors, unlike the somatic variety. [1, 11] Gross total excision of the tumor with intact capsule usually gives excellent results [3, 24]. Careful protection of adjacent vital structures is necessary to prevent inadvertent injury. Usually, it is not difficult to carefully delineate the mass from the surrounding tissues [3, 14]. There is one report of tumor recurrence in a young female following subtotal resection which necessitated repeat surgery ^[2]. In general, the post-operative outcomes after total resection are good although hormonal therapy may play a role in preventing recurrences in leiomyomas of gynecologic type ^[3].

Leiomyomas in the upper cervical spine are extremely rare in adolescent immunocompetent male.

Soft tissue swelling in adolescent male around craniovertebral junction should be extensively inves-tigated before planning optimum management.