Understanding a Cancerous Lump on the Thigh
Introduction: What is Cancer?
Cancer is a disease characterised by uncontrolled growth of abnormal (transformed) cells in the body. These cells originate from normal tissue, and mutate (undergo malignant transformation), which causes them to divide rapidly. The transformed cells form a tumour.
However, not all masses (tumours) are cancerous. Broadly, we can classify tumours into benign, pre-malignant and malignant. Benign tumours don't contain cancerous cells and don't invade neighbouring tissues. Pre-malignant (or pre-cancerous) tumours contain abnormal cells with potential to become cancerous.
Malignant (or cancerous) tumours contain cancerous cells, invade neighbouring tissues and can spread to other parts of the body (metastasise) [1].
How to tell if a lump is cancerous?
Distinguishing a cancerous mass from a benign mass involves several diagnostic procedures. Imaging studies such as ultrasounds, CT scans, MRIs or PET-CTs can be used to help confirm the diagnosis. However, the only definitive way to confirm a presence of cancer is a biopsy. A biopsy involves:
- Removing a sample from a tumour - this can be done by inserting a needle into the tumour and aspirating cells, or taking tissue samples if the whole tumour is resected (surgically removed);
- Fixing the tissue in formaldehyde;
- Staining the sample with specialised dyes that allow for visualisation of certain molecules under the microscope;
- Examination of the sample under the microscope by a pathologist, who then writes up a report confirming the diagnosis [1, 2].
There are several characteristics that can help differentiate between a benign and malignant tumours, on a physical examination as well as under the microscope.
Benign tumors are often well-differentiated and grow slowly. Malignant tumors, on the other hand, are often poorly differentiated, grow rapidly, show invasive growth with no capsule, and frequently metastasize [3]. Differentiation is a characteristic of a tumour, referring to how much cells resemble their physiological type. When a cell grows, it specialises to perform its function (becoming a muscle cell or a nerve cell etc.).
On imaging, tumours that appear round or oval with a clear margin are often benign. Masses that are of irregular shape are often cancerous [4, 5].
On a molecular level, tumours that are cancerous differ in expression of pathways related to the immune system response [6]. This may be the cause of the malignant tumours invading tissues and not being targeted by the immune system.
Cancerous lump on the inner thigh: What cancer is it?
Cancerous lumps on the inner thigh are not very common, but can occur. Often, this presents as a painful lump in thigh which is palpable through the skin. The cancers that can present with a lump in thigh are diverse - here we review the most common tumours, which can be benign or malignant.
Soft tissue sarcomas
Soft tissue sarcoma is a type of tumour that originates from various types of tissue including fat, muscle, nerves, fibrous tissues, or even blood vessels. They can occur anywhere in the body, however are commonly found on the legs [7]. These can become invasive and metastatic [8].
Intramuscular myxomas
Intramuscular myxoma is a rare benign soft tissue tumour that can present as a lump in thigh. They usually occur later in life, between the ages of 40 and 70, and are more common in females. Although they are benign, they can mimic the appearance of sarcomas and other malignant tumours [9, 10, 11, 6].
Pilomatrix carcinoma
Pilomatrix carcinoma is a rare type of skin cancer which arises from the matrix cells in the hair follicles. Therefore, it can present as a lump on the inner thigh. It can rapidly increase in size and may metastasize to other parts of the body [12]. Pilomatrix carcinoma lesions are very locally invasive, and recurrence after surgery is common.
Schwannomas
Schwannomas are rare, benign tumors, which arise from the Schwann cells, which are cell supporting the myelin sheath which protects the neuron. Schwannomas are round or oval, and occur along the femoral nerve which runs down the thigh [13].
Metastases of other tumours
In some cases, a lump on the inner thigh could be a metastasis of another tumour, meaning it originated elsewhere and travelled through the circulatory system. Then, in the thigh, the cancer cells exited the circulatory system (extravasated) and started growing as another tumour. For example, a case has been reported of a metastasis from carcinoma of the gall bladder presenting as a mass in the left lower thigh [14].
However, it is important to note that not all lumps on the thigh are cancerous. In fact, most such lesions are benign, such as cysts or lipomas. If you notice a lump on your inner thigh, it's important to have it evaluated by a healthcare professional to establish a diagnosis and recommend appropriate treatment.
Cancerous lump in thigh: Diagnosis, treatment and prognosis
As with any other cancer, diagnosing a cancerous lump in the thigh involves a combination of physical examination, imaging and histopathology. During a physical examination, the doctor assesses the size, location, and characteristics of the lump, such as whether it's firm, mobile, or associated with skin changes [13, 8, 15, 16, 17, 18, 12].
Imaging studies such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) give insight into the size and shape of the mass, and can help differentiate between benign and malignant masses to an extent [13, 15, 16, 18]. Additionally, imaging is extremely important in planning of surgery to gain insight into the anatomy surrounding the tumour.
A definitive diagnosis is usually confirmed through a biopsy. Histopathological analysis can confirm the nature of the mass and rule out potential malignant differential diagnoses [13, 8, 15, 2, 6].
Treatment and prognosis
The main course of treatment for a mass on the inner thigh is surgical removal (excision). The goal of the surgery is to remove the tumour with margins (pieces of normal tissue that are taken with the tumour to ensure that all cancerous and potentially cancerous cells are taken out) [13, 8, 15, 2, 6].
In some cases, additional treatment may be necessary - this depends on the exact diagnosis. These can include radiation therapy to the tumour site (to shrink the tumour), or targeted therapies following the molecular profile of the cancer. If the lump on the thigh is a metastasis of a cancer elsewhere, systemic cytotoxic chemotherapy is the treatment of choice.
Consequently, the prognosis is highly variable, depending on the type and stage of the cancer, as well as the patient's health and choice of treatment. Patients have shown positive long-term follow-up results after surgical excision with no postoperative complications or recurrence [13, 15, 2]. However, it's important to note that some types of cancer can be aggressive and may have a poorer prognosis. Regular follow-ups with imaging studies are often necessary to monitor for any recurrence [8].
Summary
A lump on the thigh can be cancerous, with multiple types of cancer being the culprit. It is important to get every suspicious growth evaluated by a healthcare professional. That said, most lumps on the thigh are not cancerous.
