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Background
Painless soft tissue masses on the scalp are commonly encountered in clinical practice. The most likely diagnoses still remain as epidermoid cysts, sebaceous cysts and benign lipomas. However, clinicians should be cognisant of other possible, though uncommon, pathologies as differential diagnoses. We hereby present a case of soft scalp mass which was mis-diagnosed as benign lipoma until clarified by histological confirmation to be trichilemmal cyst, a relatively common condition known to carry proliferative and malignant potential in rare cases.
Case presentation
A 56-year-old patient with learning disability presented with a lump at top of his head. Due to problems in communication, history was obtained from his mother who had been living together with the patient since his birth. The lump appeared when patient was in his late teens, and had never been painful, infected or bled. It remained the size of a cherry and it had increased in size in the last 6 months. Patient was unaware of the lump until someone commented on it. Despite repeated assurance from his mother, patient became nervous with frequent agitation, thinking that it is a punishment from God and he would soon meet his demise. He had no history of trauma or developmental defect to his head and he takes losartan and hydrochlorothiazide for his hypertension. He had no personal or family history of solid tumours. On examination, there is a solitary 4x4 cm spherical mass arising from the vertex of his skull. The mass is soft and fluctuant and partially trans-illuminable. The surface consisted of normal looking skin of the near-alopecic scalp with no discolouration, cicatration or punctum. The mass was non-pulsatile and non-tender on palpation ( figure 1 ). A provisional diagnosis of lipoma was made and when the benign nature of the lesion was explained to the patient; his mother elected to observe the lesion. Two weeks later, patient returned in an extremely distressed state and pleaded for an operation to prevent 'his brains from sticking out'. In view of the patient's inability to comprehend the situation, it was decided that the mass be removed in the best interests of the patient. The patient was offered the choice between a plastic surgery procedure (guaranteed cosmesis), or an office procedure (possible cicatration). Due to the...