Tuberculosis (TB): Given the combination of weight loss, appetite loss, and lymphocytosis, TB is a strong consideration, especially if the ovarian cyst is suspected to be a tubercular cyst. TB can affect various parts of the body, including the lungs, abdomen, and reproductive organs, and its presentation can be subtle, especially in elderly patients.

Ovarian Cancer: Weight loss and appetite loss are common symptoms of advanced cancer, including ovarian cancer. The presence of an ovarian cyst could be related to the cancer, and lymphocytosis can occur in response to the tumor.
Lymphoma: This is another type of cancer that could explain the lymphocytosis, weight loss, and appetite loss. Lymphoma can involve the abdomen and could potentially cause or be associated with an ovarian cyst.
Chronic Infections (e.g., Endocarditis, Abscesses): Chronic infections can cause prolonged fever, weight loss, appetite loss, and lymphocytosis. While less directly linked to an ovarian cyst, they are considerations in a differential diagnosis for weight loss and systemic symptoms.

Disseminated Tuberculosis: As mentioned, TB is a consideration, but disseminated TB, where the infection spreads through the bloodstream to multiple organs, is particularly dangerous and requires prompt treatment.
Malignancy with Metastasis: Any malignancy that has metastasized could explain the systemic symptoms and the ovarian cyst, if it's a metastatic lesion. Missing a diagnosis of metastatic cancer could significantly impact treatment and prognosis.
Systemic Lupus Erythematosus (SLE): SLE is an autoimmune disease that can cause a wide range of symptoms, including weight loss, appetite loss, and lymphocytosis. It can also cause or be associated with various types of cysts and can affect multiple organ systems.

Krukenberg Tumors: These are rare metastatic tumors to the ovaries, typically from a primary site in the gastrointestinal tract, most commonly the stomach. They could explain the ovarian cysts and systemic symptoms.
Granulomatosis with Polyangiitis (GPA): Formerly known as Wegener's granulomatosis, GPA is a rare autoimmune disorder that can cause a wide range of symptoms, including systemic ones like weight loss and appetite loss, and can affect multiple organ systems.
Sarcoidosis: This is another rare autoimmune disease that can cause granulomas in various parts of the body, leading to a wide range of symptoms, including systemic ones like weight loss and appetite loss, and could potentially cause lymphocytosis and ovarian cysts.